[CCIP]

Any game is possible in theory, and would be fun if made well.

In practice, this will not happen for a while. There are a few strategy games and wargames being developed that feature modern subs (from Naval War: Arctic Circle to Command Ops), but it is not very likely you'll see sub sims as such any time in the next few years. Ubisoft is not likely to develop another Silent Hunter game soon, or perhaps ever - SHV was a critical and commercial flop, and they will not be looking to spend money on this franchise. The only developer with real experience and credibility in making modern sub sims, Sonalysts, is currently not working on anything for the consumer market, instead building training software for military clients.

The most likely source from where a new sub sim might unexpectedly appear is from Russian developers - there is a decent simulation market and community in that country, and lower development costs; but to date, noone has announced any plans to work on it.

I don't think sub sims are dead or anything, and the dedicated community here more than proves that, but you're not going to see commercial development any time soon. I can almost guarantee you that you will not see a new sub sim title until, say, 2018. And then it will probably be another WWII sim. I think the market will, eventually, support new development, once new technology comes around and some of the current problems in making money from games that are not Call of Duty are resolved. But the Silent Hunter series is probably dead - long live Silent Hunter!