If I'm not mistaken by 2038, we could have reach 99% of all bitcoin mine. So that alone will speak how the price will move after that. Because the rest of the 1% will be mine up to 2140.
So definitely, 6 - 7 digits around that time is not far fetch as bitcoin will be really scarce and everyone will be fighting to get at least a satoshi. Moon by 2038 and beyond or even much earlier.
I won't speculate that much even the last piece of BTC mined. Mining all the supply means the Circulating Supply increased too so there's a chance that price will drop too. What I really looking forward is the development of bitcoin blockchain. The scalability problem is the main issue of BTC right now and so far, no concrete solution on it. A lot of different blockchain already closed on achieving it so if others can do what BTC can't, it's really alarming what will gonna happened on BTC future.