@swheaties: I think we are beyond the point of equating mobile with some fashion that is in this year but will be out next year. It fits those categories of usage, the ones you mentioned, better than a desktop or laptop does... that is quite unlikely to revert.
As for the rest, the enterprise desktop PCs, Microsoft has little reason to worry about those. There isn't much in the way of real competition. It's sad, I'd like that to change, but Microsoft knows that businesses are going to stay in the Windows camp for quite some more time... long enough that they can focus their OS energies on the personal computing market.
Microsoft is not completely ignoring enterprise anyway. They have been heavily pushing good things in Azure, and development is seeing some significant love as of late. Microsoft probably believes the OS is "good enough" and would rather focus on the auxiliary components that really make money.
EDIT: Note, this isn't me defending Microsoft. I know some of you think that's all I do, but in reality what I often do here is explain. Defense and explanation are two different things... again, many of the things Microsoft does are not necessarily things I want them to do... I would love to see them really ramp up innovation in the enterprise OS area, all I'm saying is that I understand why they don't despite them not giving me things my way.
And yes, Microsoft could very well alienate business customers and leave the door open for someone to swoop in and take their cake... but you know what, if that's what it takes, well, maybe it's for the best.