"Microsoft will purchase Ubuntu outright from Shuttleworth or they will just create Microsoft Linux"
I'm pretty sure since like 2 years they're working on at least the second, but the purchase of Ubuntu too doesn't sound that absurd to me. What really concerns me is their power as a big corporation, which could play a role in attracting a growing Linux user base to their distro. This could lead to disasters should Microsoft pollute their OS with proprietary extensions: developers writing software for Linux on a MS branded Linux would create software that "runs better" there or wouldn't run at all on others.
No conspiracies here, this happens every day in all offices when printers refuse to work with non same brand ink cartridges; so let's say tomorrow Microsoft ports a significant part of their windowing object model to Linux - to their Linux - as a closed linkable blob, then update their development systems so that one can develop full desktop linux applications with the same graphics interface model of the Windows ones. Technical issues aside, how many developers would resist the temptation? And how many of them would keep dual booting when they could build a career by working exclusively on Microsoft Linux?
This is pure speculation of course, but I have this feeling that Microsoft becoming a top Platinum Member of the Linux Foundation was the corporate way of slowly getting to the captains chair.