There is NO way in which BTC could skyrocket in use/popularity/adoption and not see a massive price rise. If we went to hundreds of millions of users or billions of users (or trillions in the case of IoT), there would be a massive spike in the price (10,000+% up from here would be extremely doable). The value of the network is tied to its use - price will track around whatever that value is. There is a question of what sort of networking power law BTC would track once it matures, but, I'm pretty confident it will scale in a pretty explosive way (if they get the scaling right).
You don't understand how mining works:

There will be halvings until 2140... it's just that at around 2030 the coin reward will be so small that the total supply will be mostly mined, but not 100% mined until 2140. By 2030 anyone holding 21 BTC+ will be RICH.
I don't think it's at all safe to say that 21 btc would make you rich in 2030, or at any point in the future ever. Bitcoin could become very successful and be widely adopted without its value skyrocketing. In fact, it's bitcoin's volatility and tendency to skyrocket/crash which is preventing it from gaining more widespread adoption.
the minimum value alone to sustain the network, and not allowing the diff to decrease, which also mean that the miners need the same profit as it is right now, is 100x the current fee
so this mean that the value by the end of the mining and the begin of the mining fee era should be 100x higher, if number of tx are the same
i'm expecting nothing less than 5k-10k range by the 2028 halving