Random number generators generally fit into 3 categories IMO:
- ad-hoc designs serving as stub to be replaced by something else if this ever happens,
- considerate designs aiming at achieving statistical quality and usable in their respective application domain,
- cryptographic RNGs of various kinds and purposes needs to fend off attack by mathematical cryptanalysis and brutal-force attack running on supercomputers.
Generally, a block-box instance of type-3 satisfies all requirement of type-2 and type-1 barring implementation efficiency details; and to be honest, there are type-3 algorithms that's already quite efficient.
The only reason I can think of not to use a type-3 RNG, would be export control - some country have restrictions on export of millitary-grade cryptography systems.
And considerate designs are plentiful, so I can't see why anyone have to settle with Mersenne Twister, which have a huge state whose only benefit would be having a absurdly long period. The other reason I can think of using it, is that people have already used it, and stopping using it, will mean losing scientific reproducibility.
So is that all the reason MT cannot be easily replaced? Have I overlooked something?