Yeah, Sega did this with the Genesis (Mega Drive) when they released the Saturn... I have seen evaliations that they lost hundreds of millions of dollars in software royalties revenues (and system sales) just like Nintendo kept on selling SNES and NES pretty long after their respective replacement came in.
So far Sony was able to sell every PS4 they have put on a store shelve anywhere in the world, I don't see why they should sacrifice the PS3 (and the services around it)
A move like that one would also alienate those who just bought one recently, think of the people who bought PS2s after the PS3 was released (about 50 million of them) they made a lot of money for Sony with the software sales, accessories etc. and probably kept the company afloat while the PS3 was building a strong lineup and a userbase large enough to sustain the entertainment division.