Actually, if this is true and Microsoft announces an external Blu-Ray player (which sounds quite more plausible than a built-in one) I´ll go with an Xbox360.
Yes, there is really the type of gamer that looks for a Blu-Ray player and a console at the same time.
More industry related: I would expect a small bump for Microsoft´s console and PS3 sales to slightly drop when the add-on is released but nothing really ground-breaking... well, if Microsoft announces a Blu-Ray player and a Wiimote clone, though... couldn´t that kill off the sales? I mean, people would be quite confused.
The same goes for a built in Blu-Ray player... hell, that would be one hell of an announcement for Microsoft. They´d literally kill their console if you needed to upgrade to the new model to play all games. But they wouldn´t be that silly...