The Toyota Corolla is, if you count all the different vehicles sold under that nameplate together, a wildly successful car. The current Corolla is also an excellent commuter, practical and inoffensive, which returns decent economy with simple hardware. That's no backhanded compliment: a great many consumers seek simple, affordable, worry-free transportation and that's the Corolla's jam.
And if you consider the 2020 Toyota Corolla, it should be that sedan's jam too. The big deal is that it'll move to the Toyota New Global Architecture, although we already heard rumors of that and it makes perfect sense. After all, the original Prius' platform underpinned a wide variety of Corolla-sized cars all over the world, up to and including our current one (in revised form). Switching to the TNGA platform already under the Prius, C-HR and 2018 Camry just makes sense.