Are there technical problems regarding the rumour? There are, certainly. However, we developers know that technical problems can be solved and Apple and Microsoft certainly have the resources to do so.
Are there business issues? Is this an unexpected move? Certainly, it is. But Apple has a history of unexpected business moves and business innovation, as does Microsoft even if it is uncool to acknowledge that.
Even if the rumour is false (I don't know) I don't find it unbelievable at all, because (a) it makes sense (b) this move would be both typically "Apple" and typically "Microsoft", if you look at the history of these companies. Hell, Microsoft started as a programming tool company.