Professor Testifies Windows Is Modular, Separable
You bring up a good point, but I don't think we have to worry about it for two reasons:
1) That would be a bit too blatant (but I still wouldn't be too surprised if MS ignored that)
2) They would never integrate OE so long as they still wanted to sell Outlook.
What you might want to worry about is the merging of OE and Outlook into a common engine that is integrated into the OS with two different front-ends (OE and outlook) with Outlook adding corporate features. But that probably won't happen (at least not while MS has the Office market all sewn up anyway).