The hd-dvd drive was such a huge success that MS wants to do it again?
There's no good reason or need for them to support blu-ray at this time. Maybe in 2012 (or whenever) with the next xbox iteration.
If they can recreate the level of sales at near the same retail prices but at a fraction of the cost, then yes. If the profit margins are fat enough then you don't need wide spread adoption and this is probably why the 360 HDD retail prices are soo high.