If the prices increase by 8x once more, then the exchange rates will be close to $120,000 per coin, and the market cap will be around $3 trillion. Is that even possible?
I'm pretty sure there is no hard upper limit. In other words: it's possible, especially in a hype.
I do worry about
sustaining it though! Currently, Bitcoin has only
12 million addresses holding more than 0.001
BTC. Anything less isn't worth the fee to spend it. Most people use at least a few addresses, so that leaves at most a few million Bitcoin holders/users.
Miners take about $30-40 million per day in block reward and fees. That's money leaving the Bitcoin ecosystem. The
trade volume is about $10 billion per day. Even at 0.25% fee on exchanges, the exchanges take $25 million per day.
Miners and exchanges together take about $60 million per day out of Bitcoin! Divide that by a few million users, and it's (give or take) $10 per person per day. That's $300 per month, and that money has to come from somewhere.
This $300 per user is a substantial drain of funds that enter Bitcoin and are taken out again, and it has to be a continuous supply just to sustain the current price and trade volume.
A price increase needs an even bigger inflow of money. To sustain this, Bitcoin needs more users, but blocks are too full already.
If Bitcoin were to double (or more), miners and exchanges take a larger share too, so even more money is needed to sustain that price level.
Note that this $300 per month is an estimate, it doesn't really matter if it's $100 or $1000, my point is still the same: a continuous inflow of dollars is needed to sustain Bitcoin.
The total for all cryptocurrencies is even bigger: miners and exchanges take their share there too.
i hear rumors that the Segiwt2x fork is going to launch this week.
As far as I know, that's a fake SegWit2x fork, aka a scam.