The strategy has not changed. Basically follow someone else (this time Apple again) and do it better. That is what they have been doing for 30 years for all kinds of products, developer tools, languages, office products, game consoles etc. (follow but improve then dominate)
The key word here is focus. They will focus on this stuff. Again, this does not mean the bread and butter PC and all that goes along with it is dead. I think it is a good thing. The PC is just fine and let it just stabilize so we do not have a moving target all the time for our applications. We have a good OS in windows 7 and great tools to use. (Let it just be for 3 years) . (I need my apps to just make money without me touching them too much)
Phones and tablets will be a moving target. Dont hang your hat anywhere as a developer here. Let things churn and enjoy the chaos because this is the fun part about having a career in this field. I get bored easily so I like new stuff. Windows phone has been all over the place so I hope windows phone 8 is close to done this time. Tablets I think have some more churn to go . Windows 8 on tablets still does not feel like it can take out the IPad. The Iphone is going to get some competition from Microsoft and Google. They are already feeling old and you can see it in the media. Watch stock price drift lower. Google and Android could really use a nicer development environment for app development. Its a bit clunky. Anyway, looks like more fun to come.