@elmer: This discussion regarding .NET 4/4.5 and XP is a perfect example of friction that may end up driving a separation between business development shops and consumer development shops.
Definitely in the short term business will stick to Windows 7 (with Windows 8 for touch scenarios -- fingers crossed) and consumers with Windows 8. Thinking further down the road when Windows 9 comes out in 2014 and businesses are on Windows 7. The divide gets larger. Then Windows 10 comes out and both businesses and consumers move to Windows 10 maybe. Then we begin the friction cycle again with Windows 11 and possibly 12 before we sync again at Windows 13.
What if during those higher friction years the business market drives the Windows that businesses use in a significantly different direction than the consumer Windows? How would things turn out if the prior years business pressure applied for XP had lasted even longer? Is there a chance business pressure for a similar situation (for say ... Windows 9 (consumer) versus Windows 7 (business)) is heightened given their previous experiences with the XP Vista/7 divide? Will businesses be even more adimant.
Hard to know. Seems like a lot of businesses forget to factor in the development discount they get for being in the same general purpose computing pool as everyone else.