Well, it's obvious from the end-time threads that most people are leaning towards a time of about 20 to 30 years after the game is released, and only a few are going for a further date. Almost everything is for that bloody spaceship! I think it's important to have more useful, non-spaceship sciences in the modern age because the time it takes to build research labs and manufacturing plants in every city by that time is the same amount of time needed to end the game, and often people end the tech tree far too early in the game. In short, the modern age doesn't offer much change right now.
Taking into acount that 20 year time so we don't have to extrapolate a few centuries worth of tech, what non-spaceship techs could civ4 have and what would they offer? My thoughts on the near future and present:
The internet tech: prerequisites are Miniturization and Syntheitic fibers. It would allow you to build a Server in any city with a Library and that would increase gold revenue and science. A Research Lab can only then be build in a city with a Server. It could also produce a Wonder with the advance of the Superconducter: The Mainframe which would put a serever in every city on the continent.
The gps tech: prerequisites are Satellites, Synthetic fibers and Internet. The gps (and other personal cadgets soldiers have nowadays like infragoggles, body armour and whatever) has greatly increased the potential of foot units to quordinate in battle, giving an upgraded unit of marines and paratroopers. Or even better a totally new unti to replace marines and paratroopers: the SAS, or Navy Seal, which is a stronger paratrooper/marine combo? This could also be a tech which gives the small wonder of a mobile-phone network, increasing gold revenue in all cities by a percentage?
The Hydrogen-fuel cell tech: Replacing petrol cars with cars run on hydrogen. Prerequisites are robotics and ecology. Gives the possibility of a small wonder, The Hydrogen plant, which can only be consrtucted in a city with some form of Powerplant (solar, hydroelectric or nuclear). Cuts the emmision of pollution from all cities (kind of like the Mass Transit only more so, because lets face it not everybody takes the metro).
The Cloning tech: Uh oh! this is a contriversial one that the fascists and commies are gonna abuse! Prerequisite: genetics (duh) and synthetic fibers. Since this is the near future there isn't gonna be any of that clone-army crap which would need accelerated growth vats and whatnot. This is cloning as we know it today. A building called the cloneing center, which can only be built in a city with a research lab. This cloneing center would increase food reasources of the city (genetically modified foods and cattle cloning). It could also give a Wonder which republics and democracies will not be able to build: the human bla bla bla, which would replace that longetivity vaccine wonder. Lets face it the democracies don't need that leg up, but commies and fascists do!
Any other ideas guys?