I would agree that Windows is nowhere near being on life support but I do think that the size of the desktop OS market is shrinking and that in the future we may see a lot more home computer users move to tablet only or something like a Chromebook.
Enterprise users are much more slow to move but as enterprise SaaS offerings become more robust we may see a lot more businesses move towards a thin-client (a la ChromeOS) and SaaS model to meet their needs. Microsoft is doing the right thing by quickly getting out in front with Office 365. If they hadn't maybe something like Quip or Google Docs could have starting stealing significant market shared but now I don't think many enterprises would bother switching if they can stay with Microsoft.
Enterprise users are much more slow to move but as enterprise SaaS offerings become more robust we may see a lot more businesses move towards a thin-client (a la ChromeOS) and SaaS model to meet their needs. Microsoft is doing the right thing by quickly getting out in front with Office 365. If they hadn't maybe something like Quip or Google Docs could have starting stealing significant market shared but now I don't think many enterprises would bother switching if they can stay with Microsoft.