Actually, I do not think so. Apple would have nothing to gain from integrating own Apps further and/or producing more of them. However, they have something to

Actually, I do not think so. Apple would have nothing to gain from integrating own Apps further and/or producing more of them. However, they have something to gain if the mail app is not good enough for powerusers and all of them buy Sparrow instead. That saves them a whole lot of developer/maintenance time and gets them 30% of every e.g. Sparrow sold. While that may not be Apples main incentive, it is definitely something I think.