Microsoft is becoming less and less of a gatekeeper with the rise of Firefox, Chrome, and Safari.
In 2-3 years when the next "version" of HTML gains the public eye, they will not have a stranglehold on the web. I'd be more worried about Apple or Google than MS (as silly as it may sound now).
I am less worried about Google because webkit, chromium, v8, etc. are open source. I think Apple has a pretty good record with open standards, but they have a big incentive to keep people buying native apps on iOS (and i guess on OSX too now). It is definitely not in their intrest to have people easily build cross platform mobile apps when the default is for people to build iOS native apps first now.
