As to the risk of waiting, I was assuming that when the Carvana offer expired, that they'd establish another offer at that time. Perhaps not as lucrative, but still good.
I've done three or four rounds of estimates and re-estimates from Carvana, Vroom, Carmax, etc. on my Honda Fit over the couple of months since my 1st Edition left the factory. They have been pretty consistent, and a couple have risen slightly. We've continued putting miles on it at a very slow pandemic-work-from-home pace, but otherwise the condition hasn't really changed.
I read the one week thing as, yes, a sales tactic, but also a hedge for them against the condition of the car changing. Things aren't likely to change much in a week, and they have to give you at least a couple of days to get things in order, but at some point they'll have enough situations where they have to honor a quote after some significant problem developed that, in the aggregate, it costs them money to lengthen the window. I don't think you should feel pressure to act right now
, before this one week offer expires, but it may be worth trying to assess the likely trend over the several months between now and September and gauge whether the market in general might be (substantially) better in late spring/summer vs. fall.
You might also want to check the logistics/order process threads - I get the sense that Pro orders are appearing sooner than the initial estimates, so you may not have to wait until September. And of course there's the option of buying off the lot, which would sound tempting if I were in your shoes.