Not just yes, but Hell yes. For one thing, this all-encompassing Mage class kills multiclassing possibilities. Mearls did say something about being able to dabble with feats. So now, not only do feats cost ability score bonuses, but some multiclassing does, too.
The Mage uber-class really presents more problems than it solves. And I never thought any of the "problems" it is supposed to solve were problems anyway. I want more classes. Class is the basic identifier of a character in D&D. The more classes there are, the better. That's not to say that they should just toss variant classes out there to inflate the class list. Variant classes should be subclasses of the parent class. Various schools belong under the Wizard class, and not as their own classes. The same with Pacts and Warlocks and heritage and Sorcerers. But, the Wizard, Warlock and Sorcerer do not belong in the same class. They're very different ideas (no matter how the Sorcerer may have started; it's more now).
Edit: After re-reading this, I've decided that they really need to come up with a better name than subclass. It's turning out to be like "Level." How many times can you write "class" in an intelligible sentence? A lot, it appears.