Get back to us when MS have a Silverlight plugin in the Ubuntu repos and allow their browser to be used on other people's OS.
Your memory must be pretty short, its only recently that Adobe have released new flash version to Linux at the same time as OSX & Windows, and even more recently that they released a 64bit version. Companies can change.
I'll be surprised if they follow the lead that Adobe set for them but it's still possible. Indeed Silverlight may well be part of the reason that Adobe finally pulled their finger out and got serious about their flash plugin on Linux.
Companies can change for the better, first they have to want to though and there's no sign of that with MS yet AFAICT.