We can send space ship beyond event horizon and still care about what is going to happen on it after it crosses event horizon, despite this being utterly irrelevant to our genetic fitness in causal sense. If we are capable to develop such preferences, I don’t see any strong reason to develop strongly-monoverse decision theory.
Multiversal acausal trading is just logical consequence of LDT and I expect majority of powerful agents to have LDT-style decision theory, not LDT-but-without-multiverse decision theory.
There is a difference between adoption as in “people are using it” and adoption as in “people are using it in economically productive way”. I think supermajority of productivity from LLMs is realized as pure consumer surplus right now.