The story I'd heard is that shipping the units with blu-ray drives would put them in the poor house. The cost of making a PS3 with blu-ray is supposedly upwards of $900. To stay competitive they'd need to keep their msrp at around $400. That's too much of a loss per unit. Sony's even been polling PS2 players about how important HD is to them in the next gen consoles.

I'm sure it'll be available at an added cost, but I wouldn't hold my breath and expect to get it for $400.