I have no doubt that one day 1 BTC will be worth $100k, but I also agree that such high price can not be held for more than a few days, same as $20k back in 2017. We should also consider that on the way up to $100k a big sell pressure should be expected, some people will be happy with a much lower price and I think that almost everyone will take profits on $30k or $50k.
From today's perspective it is not easy to imagine that 1 BTC can go up to $100k, but this is only ten times the current price. But I also think that something big will need to happen to start next big bull run, and next halving is not end of Bitcoin mining or anything like that.
That's certainly true, mate. After all, crypto's movement is price behaves much a like a rollercoaster. There will always be ups and downs. But, I believe that a new bottom in price will be established within a couple of years from now. The scarcity of the Bitcoin supply, as well as, increased mainstream adoption (because of the Lightning Network and other features), will allow Bitcoin to reach new ATHs in price. It's evident that many people who bought Bitcoin during the bear market of 2018, will sell most of their coins within the next upsurge in price across the market. This would trigger a decline in price across Bitcoin and other leading cryptocurrencies, at least in the short term.
The bright side is, that Bitcoin will retain its value no matter what. As each halving event takes place every 4 years, Bitcoin will rise in demand like never before. I believe that even after all Bitcoin have been mined, miners will continue to support the Blockchain (as they'll earn from network fees instead). By that time, Bitcoin's prices are expected to be a lot higher than what they are right now. Something like $1m per coin within 2100 (the year where Bitcoin mining is expected to end) seems like a most likely target.
Nonetheless, with the fast-growing pace of Bitcoin, the goal of $100k per coin might reach sooner than we've thought. So many exciting things are yet to come (Lightning Network, atomic swaps, etc) which I believe will increase mainstream adoption by 100%. In the meantime, we should buy and hodl Bitcoin as much as we can while prices are still below 2017's ATH of $20k per coin. You'll then see your investment multiplied within a few years from now, without much effort from your part. Just my opinion