I asked the lead service technician a few days ago when I was at the tesla service center for something else this specific question:
Me - " I hear that people who purchase Full self driving option get the new Hardware version 3 computer. How hard is that to swap, exactly?"
Tesla lead service center technician (NOT advisor, the head Technician) - " Yes, thats correct about the new computer swap for people who have full self driving. We are not sure when that will happen, but are told that it will be free for those who have that option. The computer actually sits behind "here" (pointed to bottom of glove compartment area). Its not too bad to swap out. Considering time to get to it, remove / replace, put things back, and also program it.. update the firmware on it, I would say its a 1/2 day job."
So, there is someone beside elon saying that ( a person who would be directly doing it, and being in charge of other people doing it, who had no reason to lie to me about how long it would take).
Of course, he could be lying to me (I doubt it though, given how the conversation was going, we had a very cordial conversation about other things), and I am just some random guy on the internet. I believe him though on both things (that he was told it would be free for people with FSD and the time to swap).
Its also possible for things to change... for example, I am still not sure I will get the new hardware if I buy FSD when its 2k. I am convinced that those who pre bought it will, but not sure that people who buy NOW at the lower price will. I also believe that swap would be "eventually" as in next year sometime, not "soon".