Will is be US-based like Mozilla, or will it be somewhere else, like Europe?
A couple of foundations have moved away from the US in recent years, for example the Eclipse Foundation (Belgium) and the RISC-V Foundation (Switzerland).
It seems foundational (if you'd forgive the pun) to know under what laws the foundation will operate, and who (if anybody) will be excluded from taking part in the project because of sanctions regimes.
On the software patents aspect Mozilla doesn't have any patents it would need to give to the Rust Foundation so I don't see this being relevant either.
It's interesting how many commenters are saying "not in the US". The US is very strong on rule by law with regards to corporate law and nothing has really changed here. The court systems are also quite good.
That seems to depend on who's "rule of law", and the flavour of the day.
The US really doesn't seem stable in any kind of positive way, nor seem to be heading towards that improving.