I didn't bother to comment on this rumor before, but I've seen people re-posting it lately and I hate to see how it's being used against the game. There's a bit of truth to the rumour in some ways, but the info from that link is inaccurate.
AvP3 came about after a successful prototype game. Set on Earth, it was loosely based on the concept of a lone Predator tracking down Aliens. When a game of AvP:R was asked for there was no time to do a 360/PS3 game, so the PSP game of AvP:R was started, with production of the full AvP game starting a little bit later.
So, to summarize, Rebellion did create an AvP:R 'esque prototype where you could only play the Predator, which did its job and got them a greenlight to make a different full AvP next-gen game and that was it.
The prototype, PSP game and AvP3 are not related beyond that. With exception of the PSP game
introduction cinematic which was all rendered from the prototype.