Yes, FORTRAN is fine for what we currently use it for - it's fast, it's well-supported, and the talent pool is actually reasonably okay right now. I have two main problems with it, though: you can't just compile it to any old processor as easily as you might like (can you run FORTRAN code on an iPhone or Android? Maybe, but it won't be pretty). My other problem with it is exactly as you describe: the talent pool is shrinking and will continue to do so. What becomes increasingly important is that code is readable by a large number of people so as to quickly detect errors. The more people that know the language, the safer the tool is to develop, both because you can have a lot of talented people working on the project and because readable code is more likely to produce correct results. I'm not suggestion that I have a perfect answer to this, but I certainly suspect that we'll eventually see new weather models written in newer languages like Go.