Yes, your 4850 will still handle mosts games at high/very high settings, give or take, provided you go easy on the AA.
However, if you do score a 24" or 27" monitor, then you're looking at a graphics card upgrade. Having said that, I always advise people to spoil themselves when buying a monitor. It's probably the single most important interface between you and the whole of computing (be it work or games), and I yet to meet a single soul that has regretted buying a big/good monitor.
There is a fixed amount of intelligence on the planet, and the population keeps growing :(