PS4 won't have a huge following till several more years.

It's been statistically proven over the years that the majority of consumers won't buy consoles more than $300. If 60% of the console population is still on PS3, there's no way Square would cut support. They'd be throwing away so much money.

So until PS4 has had several price drops and is around the $300 mark, there's pretty much no chance of it passing PS3's userbase.