I sincerely hope not. I think the problem is the way the App Store makes companies race to the bottom in price. Why can't they charge me (and the other 1M users on the waitlist) $1 a month as a subscription fee? I realize things will not even out completely (not all 1M users would pay $1/month), but I really do think it would be enough to sustain a true business. When these companies get bought their true feature set (and thus user base) dies out. Just look at what happened to Sparrow...
Does anybody recommend a similar mail client for Mac? I've just been using Mail's flags to maintain inbox zero but am always looking out for a better alternative.