PC Builder Professionals?

In my experience the obsolescence of a PC is mainly down to the processor size which in turn is limited by the motherboard. Other relevant components can be easily upgraded within this envelope. Furthermore there are major leaps forward leaving existing machines totally obsolete with regard to power hungry applications like games. Is the state of play such that it is best to wait before spending about �1000 on a new machine, or is there nothing earth shattering on the horizon at present? I cannot afford �2000+ for a specialist games machine. Thank you.