The website expressly states that if you purchase Full Self Driving Capability, you are eligible for a free upgrade to the 3.0 computer. My install is tomorrow, they haven't sent an "estimate" yet, but I expect it to be $0. Whether or not that has changed now that the upgrade is $2k total, I dunno. But It still says it on the website so it would be an easy dispute. As far as cameras go, the Beta should function as intended after the computer upgrade, if your cameras aren't right I would think that would be replaced, maybe at your expense, if damaged.
I've had my car almost 6 years now and it is hard to fathom dropping $2k on software on a 6 year old car. I have no reason to get rid of the car though $2k to breathe new excitement into it is well worth it to me.
I wouldn't upgrade on the assumption that you will get to transfer in the future. Buy it for what it is. Youtube, FSD Beta 4.3.2 (or whatever) and thats what you are buying