WinRT failure won't directly affect MS
Their stock price is still high! Look here. And MS has billions of money with them, And dont forget about their other products, XBOX, WP8(Im not sure about this) and the "full" Windows 8. That plus high MS stock will surely keep them afloat.
XBOX = With the new games, by Q4 this year the XBOX would've sold a lot, It is highly doubted that it won't since its already popular.
WP8 = With it gaining more attention, It might sell a lot, especially because of low hardware costs and the easy to use interface.
The "full" Windows 8 = OF COURSE it will sell, Its the known real Windows, duh!
High MS Stock = The link I provided earlier says it all, It will just get higher and higher.