Windows 7 will probably get its "foothold" on the consumer market the same way Vista did: when people buy new computers they get Windows 7. I speculate that the vast majority of Windows users are simply running the same O/S that their computer shipped with, whether that is XP, Vista, or even ME (I've been shocked by how many people I know are still running ME (in a vague sense of the word "running")).
Of course that doesn't apply to techies like us, but when you hold mass market share you have mass market demographics.
As far as businesses upgrading their workstations to Windows 7... no way. Windows XP is pretty stable (they've been improving it for like 8 years, it oughta be) and there are few compelling reason for a business to invest in Windows 7. The only way MS will get Windows 7 into the business market will be to force it (via OEMs or by stopping support for XP/Vista).
I think Microsoft's outlook (pun not intended) is pretty gray in the O/S market.
EDIT: changed "no" reasons to "few" as trezor pointed out at least one reason I was unaware of.