AMD's recent acquisition of ATI means that they are now able to offer CPUs with built in GPU. This means you main processor may also have some serious graphic muscle built in.
It seems in response to this Nvidia may be entering the Processor market. It is still just rumour but they have recently taken on new staff that have in the past specialised in CPU design which sniffs of an Nvidia chip at some future date.
Whether this poses a threat to Intel or AMD remains to be seen.