Some games can easily do 4K even with a 7950, e.g. DotA 2, etc.
Problem is, if you want new games to do 4K (maxed @ 60fps), you basically have to drop £1000 every 2 years or so for 4K. If you don't want to be in that situation, then forget it. Imo 1080p @ 144hz is much more enjoyable for general gaming anyway.