I think, we all would love to hear an official Tesla statement on the FSD option, whether it is transferable or not, and how a new perspective owner should find that out since Tesla will not discuss any details if inquiries come from not the current owner.
I could be wrong but I was almost certain that the MCU2 cannot be upgraded/retrofitted instead of MCU1. (Details are
here )
As I said before, In my eyes, to get Tesla cars a full autonomy selling the FSD option was a crowdfunding effort to get an additional $3K from excited buyers. Nobody knows when a full autonomy level 5 would be legal, and maybe (just maybe!) never in my car lifespan!