Well I was writing in the sense that the Sony bind goes without saying, John - and I'd presume that extends to MGM even though Sony only own a 20% share in the company. Whether those with the greater share in MGM wanted to release on HD DVD as well if they saw potential to make money I'd be interested whether Sony could actually do anything to stop them.

I can certainly share the belief that Sony and Fox would be the last to cling on with dear life to the format if it begins to dwindle however, but Fox still isn't bound by any agreement exclusively to Bluray. It's there by firm choice over the SPDC/BD+ issue... unless of course they are that alleged studio Sony is rumoured to have paid in order to gain their full support.

In similar ways to Fox pledging their support for a specific reason, Disney see its extra potential for offering a further 20gb of storage over its competitor as an advantage and therefore back it by choice too, but it remains mere choice and choice alone. They've left themselves free to migrate so like I say, there are not many - beyond the obvious - eternally bound to the format if they wanted to spread their content elsewhere sooner rather than later.