It does seem Apple may be assembling a new team for ground-up mobile GPU design, but I won't hold my breath that Imagination will end up getting displaced inside iPhone and iPad.
I don't want to get into a CPU vs GPU complexity argument. (Or rather, I do
, but this is neither the time nor the place). I'll just point out that there is a fair number of suppliers that are broadly competitive. Qualcomms Adreno guys, ARMs mali group, Vivante, Intel, AMD, nVidia, ImgTech - they are all players and some of them with very limited resources, particularly compared to Apple.
Also, Apple doesn't start right now. They have been actively recruiting for a fair while, so just how far along they are is difficult to say from the outside.
I don't see that there can be any doubt that (premium) mobile graphics is the target. That's where their money is, and in the greater scheme of things it's the only really interesting market.
I was surprised by how outspoken the job offers were. They send a very clear message to applicants that Apple is putting its weight behind this effort.
Before I saw those statements, I assumed that they had "contingency plan" development going on, which would quite possibly only ever get visible to the outside world in the case of their relationship with ImgTech going sour or being disrupted in some way. (That this was a concern of theirs was apparent already when they bought their defensive stake in ImgTech.) But their Orlando effort seems far too substantial to simply be a back-up plan.
That said, just as with Intel and the Macs, as long as it makes sense to them to continue with their current partners, they likely will.