The cancellation of the "PlayStation phone" leaves a very intriguing "what if" scenario, because going by past history such a phone might well have been based on the same unified Symbian platform that Nokia is going to use on future N-Gage phones.
That would have meant a direct face-off between Nokia's N-Gage platform and Sony Ericsson's gaming platform, which in theory Nokia would have wanted to avoid because many might have chosen Sony Ericsson's offering instead. The competition would have been especially fierce (and good for gamers) because phones using the same OS version would have offered a similar set of features and similar interface.
However, such competition might also have helped N-Gage, as porting between the two platforms would (theoretically) have been extremely straightfoward thanks to their shared OS and software platform. Third party game publishers might well have routinely released games on both formats, and perhaps as straight Symbian games too, because it would have been so easy to do so.
...but all this is speculation of course, and pointless speculation too as the PlayStation Phone doesn't look like happening after all.
Or does Sony Ericsson have plans to release a gaming platform without the PlayStation name? No one knows.