If traditional game companies discover that they can craft games with a guaranteed revenue stream for an audience that is both comparatively untapped and indifferent to the complaints of the hardcore gamers, you bet your ass they'll jump ship. No rationally acting company would do otherwise. Particularly public companies beholden to shareholders.
There's nothing preventing companies from making good games (subjectively speaking) for mobile devices. But if consumers are indicating with multi-million monthly revenue numbers that they're willing to pay for shitty IAP driven 'gameplay', you can expect a lot more of them.
Even here on GAF, bastion of gaming purity (cough), you'll see plenty of people bemoaning their weakness as they purchase a bunch of shittily overpriced DLC for some game or another. Extend that behavior to a whole different breed of consumer who have been raised on their mobile games demanding payment as a matter of course and it's easy to see where Candy Crush or Puzzle & Dragons numbers come from.
But more interesting to me is what it means for series that could potentially end up as a 'normal' handheld game. Will we see cross platform releases? Or will they just straight up target ipad/android devices?
In a generation or two we're going to have pocket super computers on our phones, and at that point the limitations come down almost entirely to input mechanics and creativity, not raw horsepower (they're already at a point where a lot of what we consider to be traditional handheld games will work just fine on almost any phone, much less retro or old game rehashes/rereleases).
As long as there are billions of dollars to be made on traditional console and pc games, they're not going anywhere, but I'd expect every major publisher to have several devs working in the mobile space in the near future, if they don't already.