I agree physics engines get less maintained and we need to do something.
We also see build issues between versions of ammo : AmmoJs SoftbodyImpostor - "b._free is not a function" error - #13 by ruzrobert
Adding a new physics engine while still supporting existing ones might not be a good idea because of lack of time.
This is a discussion we will have for babylon.js 6.
Physx is, IMHO, the best available on native and the wasm version needs some tests to see how stable it is. Do we need to maintain a build on our side?
The Babylon team will gather in June. It will be the perfect moment to discuss what we want to do. @PirateJC @Deltakosh