The ownership of Blu-ray is quite a grey area.
Panasonic (in-particular Mitsush*ta) actually developed the technology itself based on a previous digital format that had more limited commercial success.
Sony however have the patents.
Control over who is accepted for license is in the hands of the Consortium.
So who actually owns it really is a grey area as I said.
For all intended purposes though, you can simply say Sony own it given they legally are the ones who have final say over what does and doesn't happen with it.
However this CAN NOT lead to refusing to let competitors using a format if they use proper routes. For example Samsung who currently provide Sony with their recent HD-DVD and DVD drives, are part of the Blu-ray Consortium and are allowed to supply drives to whoever they choose.
As Blu-ray itself doesn't use any propriotry encoding format past the BDi system, which is technically just a java program that'll run on anything capable of using JVM; again Sony really don't have any way to physically stop Microsoft using BD technology.
In-fact if anything they wouldn't stop it.. because it's one of those things you can hold over another company at big game events like E3/TGS/GDC.
This all said, Microsoft will NEVER replace the internal drive.
Reason for this is quite simple, currenly ALL Microsoft Xbox 360 units released will ALL run anything released for the format. Sure a few games state requiring HD (which unlike what many believe(d) actually stands for Hard Disk, and was only required when the 64MB Memory Unit was the only one available)
Microsoft's stance on the 360 has always been no matter the package you purchase you're technically buying the same machine, not something cut-down.
This all said, Microsoft ARE as-in not a rumour, there WILL BE a Blu-ray add-on drive released in Holiday 2008 to replace the current HD-DVD drive; which are currently being lowered in price many places in order to get rid of stock.
Microsoft had said from the start that, although they believed that the HD-DVD format would win; they didn't want the consumers to be forced to have the option of one of the HD-formats at their own cost.
I personally felt it was a good stance, and still do. They did mention they firmly believed that DVD would be more than enough for "next-generation" games. I also firmly feel this is the case.
So far we've seen a handful of PS3 titles utilising the extra space of the BD only to find very similar image quality and game length. I've yet to really hear anyone complain about Blue Dragon or Lost Odessy both coming on 3+ DVDs, and wished they were only one disc.
I never heard this complaint from people who used the GameCube where lots of games were multiple discs. Just isn't a big deal for gamers to get up and change a disc ever 10-15hours of gameplay... never has been, doubt it ever will be.
Then on the flip side you have a monumentally huge game like Mass Effect fitting on a single DVD, which blows away many other titles for gameplay length and content!
If I start to see titles getting shorter due to disc space, then I might agree that DVD has run it's course and the 360 being tied to it is a bad thing; but I've yet to see anything do that.
We'll just have to wait to see say when an FPS either is half the length of a PS3 version or comes on multiple discs when I will agree that the extra space of BD for games doesn't simply make developers lazy.
It will also have to come from a studio outside of Japan who seem to not believe in compression. As the only games I currently have that are multi-disc basically are Japanese-RPGs
Still people would also have to proove that gamers are actually to lazy to move 10ft to change a disc. As we've been doing it for over a decade now, really don't see a problem.
Hell I have some PS2 games that are up-to 5 DVDs. Again those are from Japan though.
