Microsoft is already eating RIMs lunch without a buy out. A lot of RIM's enterprise software is tailor written for the old BBOS and wouldn't do MS a lot of good.
Which is why RIM is trying to move their expertise into areas such as Mobile Fusion, allowing administrators to managed BYOD in the enterprise. Imagine BlackBerry BES services on your personal Android or iPhone, so you can access your company's assets in a secure manner. It's something RIM is working towards, and is honestly something that Microsoft's culture wouldn't allow.
