Look, it is certainly in the realm of possibility that Apple and Microsoft would eventually merge, assuming a number of factors fell the right way, first of which is that either Google or Samsung push into the monopoly territory, but that is still very far off, much more than just 5 years. Money Map Press analyst Keith Fitz-Gerald thinks that it is "absolutely possible" that Apple and Microsoft could merge within the next 5 to 10 years. Beyond that, his reasoning is a bit obscured:
It seems that Fitz-Gerald is saying that because both iOS and Windows Phone work well for an older demographic, and because both are focused on content and security (as if no other platform has the same focus?), that a merger is possible. And yes, it is definitely "possible", but at the same time it is "possible" that Larry Page could sell Google to Yahoo for $3. "Possible" just means "not impossible". It's a word designed to get an analyst some attention from the media (which it has done successfully here), but it is not a word that even crosses the barrier into "likely", let alone "realistic", which are very different propositions.
It is definitely interesting to consider a world where Apple and Microsoft need to merge to survive, but it's hard to imagine the events that would need to unfold for that to happen.