Though I would do this, for sake of keeping track of things.
Campaign & Maps:
New Campaign - It will consist of 20 missions on 10 new maps. Campaign will be story driven.
Larger Islands - Average island size is about
twice that of Tropico 3. Max island size is about
quadruple that of tropico 3.
Tutorial - Multi-stage tutorial which details the basics of the game as well as some of the finer points will be present.
Buildings:
20 New Buildings - Stock Exchange, Shopping mall, Aqua Park, Mausoleum, Chemical Factory, Roller Coaster, Fire Station and Horticulture Station. E3 coverage buildings (tentative) : Ministerial building, Salt Mine, Space/Cosmic Needle, Plantation, Museum of Modern Art, Zeppelin Hangar, Nuclear Power Plant (

) (Community discussion on the subject:
http://forum.kalypsomedia.com/showthread.php?tid=8826)
Building mechanics - Production facilities will have the option to import their raw materials. Some buildings may require blueprints before construction (feature possibly restricted to campaign/story mode only).
Road Construction - The way the roads are built is supposedly improved.
Game Mechanics:
Interactive disasters - Including volcanoes, tornadoes, fires and even a tsunami. All disasters are visually represented in game and most of them allow for some kind of player interaction beyond just rebuilding what was destroyed. They will be liked into the Fire Station building, such that you can prioritize which buildings are serviced first, and even pay a helicopter to get the job done instantly.
Council of Ministers - Can be run as a democratic institution, as people's committee, or an outright military junta. Allows selected citizens to be appointed to ministerial posts in the government to help push through more controversial decisions. Can be foreign experts or Tropicans. They can cause trouble depending on their competency and how corrupt they are; If they aren't competent for example they may give some very obviously dubious advice (with consequences should you not follow it). Note that a skilled minister offers quite the advantage; For example a competent economic minister will be able to get Tropico better deals for her export and import prices. You can also blame them for your own mistakes.
National Agenda – Receive objectives from Tropican factions, foreign geopolitical powers or opportunities relating to current island events such as ongoing disasters. They are similar to quests in RPGs.
Trading system - Import and export goods to/from other nations to boost your economy or production. Foreign powers can set trade embargoes on certain goods.
International Relations - Europe, China and the Middle East. Each superpower has its own unique agenda. Europe is deeply concerned about human rights on your island, while the Middle East is deeply worried by the price of oil and how you affect it. China on the other hand is more concerned with business and trade opportunities. The new superpowers will not be able to invade your island, but they can do damage in other ways, like imposing embargoes and other penalties.
Foreign Investment - The Stock Exchange building will serve as medium for offers of foreign investment for the construction of private buildings, which go bankrupt if they do not have enough resources, or workers to keep up their profits. Their owners will also be able to set wages as they see fit.
Crime & Punishment - The citizens of Tropico may become criminals and start committing armed robberies and even murder. Your policemen will try to arrest them or shoot them down.
Agricultural Policy - The Horticulture Station can, to an extent, affect the way agriculture is treated on your island. It can be used to plant forests, turn all of your agricultural production organic, or you can dabble in the science of genetically modified corn.
Flair/Fun:
Interface - Updated, slicker, and slightly reminiscent of Tropico 1.
Presidential Traits and Outfits - There will be new El Presidente outfits available for select editions of the game (content to be revealed at a later time). Tropico 4 also features a new Traits system that allows character development over the course of the campaign
Characters representing domestic and foreign interests in Tropico.
Radio Announcers - Juanito is reported to be on a work stress related vacation. Some long lost friend of El Presidente, familar to the old guard of
Tropico, will be taking Juanito's place.
Online/Community Related:
XBOX 360 Version - Confirmed that the game will also be on Xbox 360.
Facebook and Twitter integration – Post live Tweets directly from the game or create posts automatically upon completion of missions, unlocking achievements, etc. Store and display achievements on a Tropico 4 Facebook page and see their how your Dictator rankings fare against other players (PC only feature). These features can be disabled without any gameplay consequences. There will also be a facebook application that tracks your play style; ie. Militaristic, Capitalist, Democratic, etc.
Leaderboards- Accessible in game for both the campaign and player created challenges.
Screenshot gallery – Take screenshots of your tropical paradise and share on your Facebook page (PC only feature)
Terra-forming / Online Challenge Overhaul - The challenge editor has been made simpler. It will be possible to mold challenge created islands more; The tools and interface for challenge creation have been totally redone and give many new options. Exactly how much in the final product is however currently unclear. Currently confirmed: Modifications on the terrain and adding/removing resources, crop and beauty markers. It will also be possible to place the starting buildings on the island.
Release:
Release date - Sometime in August.
Post release support - There are plans to have a good deal of post release support including free dlc in addition to the standard patches and updates.
Price - 49.99$ for Xbox-360 and 39.99$ for PC.
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Here are the sources:
http://www.neoseeker.com/news/14609-el-p...tropico-4/
http://news.bigdownload.com/2011/01/04/i...games-abo/
http://www.gamedaily.com/games/tropico-4...to-august/
http://www.gamersguidetolife.com/2011/05...cio-4.html
http://www.strategyinformer.com/pc/tropi...rview.html
http://www.facebook.com/tropico4?sk=app_128953167177144
http://www.gamingbits.com/xbox-360-news-...w-e3-2011/
http://www.gamespot.com/pc/strategy/trop...tag=images
http://e3.gamespot.com/image_viewer/6318...%3Bthumb;1
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If I am missing stuff, or have said something not explicitly confirmed please feel free, and obligated

, to post the corrections. I'll update the post in consequence. Make sure to include your references.