Pascal is likely to be presented in April at GDC. General availability may or may not be around the same time. If it is, it will probably be the "new" titan, but you never know.

I struggle to run 1x 4K display on a 6GB 980Ti in some games. There just isn't enough GPU power for it, like its at 99% all the time. Memory usually runs at about 5GB so that side is OK. If you are running multiple games at 4K then that would be hard work for a single, or even a pair of 970's.