You can speculate the price of Bitcoin 10 years from now but no way you can calculate it. There is no such mathematical calculation that will send you exactly 10 years from now, not like we solve common mathematics problems. It is better for you to speculate then rather than bother your mind thinking about what will happen a few years from now because you will just fail. You can't project where it stops and how far it reached, even Satoshi can't make it.
Speculate the Bitcoin price is okay, but don't trust it. Honestly, I am not interested to speculate the price even if for the next 10 years, 20 years, or more. I think it is just wasting effort, speculating Bitcoin price with too big time gap will be almost no accuracy. I prefer to speculate on the Bitcoin price for the next months or the next year, it still makes sense. Anyway, surely speculation has no certain mathematical calculation, it is just like a guess.