[Apart from Inside Out and one other project], [e]very other upcoming Pixar feature that’s been announced is a sequel. Finding Dory in 2016, Toy Story 4 in 2017, and (as yet unscheduled) The Incredibles 2 and (brief shudder) Cars 3. For those keeping track at home, that’s a total of four announced sequels and two announced non-sequels. It’s tough to think of a more conspicuous advertisement that the creative wells at Pixar are running dry.
Dissenting POV here. I don't think it's that the plenitude of the creative wells that are the issue here. I think it's more a question of the effort-to-payoff ratio. If you know people are going to line up around the block for something with a given name on it, you lean that much more towards creating such a thing as a time- and cost-saving measure. Yes, cost-saving — the cost of not having to go through the trouble of iterating until you come up with something original that works, and the cost of worrying about how well it'll fly with an audience that knows nothing about it. Nothing succeeds like the same old success.
What makes it most egregious in Pixar's case is how this was a creative team that stubbornly resisted doing that for a good part of their life. They favored creative risks that paid off, and while they haven't abandoned that entirely, it's become that much less a part of what they do as they can turn far more easily to monetizing their existing IP. Doubly so with them being a subdivision of Disney, with all of its concomitant demands for monetizing properties over taking creative risks. I imagine after getting their fingers burned with John Carter, they're becoming all the more risk-averse.
Creativity is everywhere if you look for it. The problem is that most of us don't have the time to ferret out every single truly creative thing going on around us, and so we rely on easy ways to learn about it: word of mouth, trends, big corporate distribution systems, occasionally a critic with good taste. But for the most part, we just wait until something interesting is pushed in front of our noses by others, a process that is done at such scale that it can't help but be costly, and so it's no surprise the stuff pushed in front of us emerges from a risk-averse business model.
In the end, then, it's all empowered and maintained by our own unwillingness to take risks. If you seek a monument to all this, look inside you.