I was able to switch my Solar Roof token for a HPWC. Initially they said that I couldn't, as my 2 referrals were from before they changed the program (even though it was an extension vs new program). Then later they came back and said that because my 2nd referral took delivery in the second program extension window (when they added the HPWC option) that I could in fact exchange the solar roof token for the HPWC (or I could take a second Radio Flyer Mini S). I opted for the HPWC even though they aren't shipping yet, so I've have been "added to the list" to get one when they do.
Don't expect to see it before well into summer, but that's just me assuming it'll ship in "Tesla Time".