I'm all for taking this mod and adding something like a Neomodern era before the Futuristic one, but whatever you do, do NOT go the route of Next War. Next War was a great idea but as implemented very poorly.
If you do decide to do it, here are some things that could be implemented that are being developed or experimented with right now:
1) Metamaterials. Materials that capture and circumvent light, making them completely invisible, but also rendering them blind. Can still detect with and be detected by radar. Possibility for new land-based stealth units here.
2) Antimatter. Half a pound can create as much energy as a 50-ton nuclear bomb. It exists, but we have not yet created enough of it to be useful. That could change in the future.
3) Genetic Manipulation. In short, the ability to eliminate genetic diseases and crater superhumans, or conversely, develop new deadly bioweapons.
4) Cloning. We have cloned rabbits. We have cloned sheep. Humans could be next.
5) Bionics. Prosthetics are becoming more and more advanced, and can already behave like a normal limb. In the future, they could be stronger, faster, and just plain better then normal limbs.