Everyone will be buying bitcoin at that price. Bitcoin is still bitcoin and it can go even higher so these is no point to stop buying it at a high price.
People who DCA do it all the time because they keep buying Bitcoin despite the price.
Despite the price bitcoin is bought only because the long term selling price may be good and the profit would be high. The main reason is the long past charts of Bitcoin that show big changes from low price to high price and cycles that happen.
However 100k is a price that practically has not appearer in the market yet but we will have takers at that price - consider if the price remains static at that then this would be common.
Always fractional buying is possible because a Bitcoin is divisible upto 8 decimal spaces. Don't let the price on 1 whole bitcoin intimdate you.
Definitely going to be a normal thing when it reaches there. People bought bitcoin when it was just a few dollars, people bought it when it was few hundred dollars, they bought it at few thousands, and there were people who bought it at 60k+ as well. So that shows that no matter how high it gets, there will always be buyers who will make some profit and will want to invest into bitcoin without a doubt.
It is not going to be too simple and we need to be entirely sure what's going to happen before we make a decision like that, but that doesn't mean that we are going to end up with a bad result eventually. I hope that people will realize that buying bitcoin at no matter what price, is a good idea and we could profit from it.