Well, as Ben
reported the PS2 earned EA $73 million in their recent three-month earnings while the PS3 only scraped together $17 million. If that's reflective of other publisher's earnings there's no reason to stop yet, especially as Sony can essentially use it as a source of income while they still try to gain ground with the loss-making PS3.
I can certainly see the PS2 still being strong this time next year. After that will depend entirely on the PS3 uptake and development costs weighed against potential profits.