According to French gaming site JV247, Sony very nearly included backward compatibility in the recent firmware update for PS3 but changed their mind.
Being able to play PS2 games on the PS3 would grant the next-gen console a significant boost in popularity. Xbox 360 already enjoys this feature, leaving Sony late to the party.
Apparently this morsel of information arose when they were chatting with a French videogame publisher, where JV247 was also informed that compatibility would be included in firmware if Sony decides to sell PS2 games over PSN. Makes sense.
No confirmation from Sony.
Source: PSU