I would say that ImgTec now have enough high profile partners in other markets (Hitatchi, ARM, STM (they're still in it for set top) to ensure the future survival of the company. Meta and MBX (possibly combined?) are two VERY important products for the whole industry, so I'm sure these companies will ensure the continued survival of ImgTec as a whole.
As for PowerVR in the PC space, well, that could go either way. I suppose PowerVR Technologies will continue designing the IP and it will be a case of just waiting until the right partner comes along. NEC obviously weren't. ST looked very hopeful at the start but turned out to be just as unenthusiastic as NEC. VIA are a possibility, but god knows whats happeneing there at the moment.
The interesting thing is that PowerVR still maintain that they will continue to be an IP licencing company, ie they are never going to make their own chips. So lets not forget that should they so desire, NVidia, ATI, Matrox, anyone, could license PowerVR technology off them and create it under their own brand. This is what I would assume ImgTec is hoping for in the long run. If IMR's do run out of steam at some point, then the large IMR companies named above will need to develop alternative solutions. Assuming they go down the TBR with HSR route, they have the choice to either attempt to develop it on their own, or license the technology off PowerVR.
This is what I presume PowerVR are hoping for. Although it must be stressed that that would be a long time coming yet.
Many people assume PowerVR operate the same way as NVidia, ATI etc. but the plain truth is that they don't. Their business model is completely differenent, and their attitude towards the industry reflects this.