In the mid-credits scene featuring the Council of Kangs, it’s said that the variant Ant-Man just battled in the Quantum Realm is dead. The Kang who resembles Immortus claims this is true and rejects the others’ doubts. You’d think an assembled legion of such powerful beings would know definitively one way or the other, but it’s hard to say for sure if the exiled Kang is actually gone for good.
It isn’t really made clear what happened to him. When Scott douses the multiverse drive in Pym Particles, it appears to overload, and then Kang simply vanishes into it. It’s possible that the energy emitted by the device vaporizes him on the spot, or that he’s pulled apart into a million different universes, torn asunder for all time. However, it’s also possible that he’s simply teleported somewhere else — somewhere he can lie in wait for the perfect moment to strike.
It’s difficult to predict whether or not the exiled Kang will return, because there’s so much still unknown about Phase 5. “Quantumania” positions him as a particularly dangerous Kang variant with a unique motivation, but the franchise could just as easily replace him with the Council of Kangs. A story about the exiled variant coming back for his revenge might be interesting, presenting a more singular force with which for viewers can invest themselves. Alternatively, it might be way too complicated.