This would be possible if the person is earning way higher than $60k per year or luckily Bitcoin price drops down to $50k or they would have to increase the yearly intervals they have set to accumulate the 4.5 Bitcoin.
I am not going to presume that the bitcoin price is going to drop... sure it might, but we should not be making our plans based on things that are out of our control.. Yet, each of us should be able to figure out how much of our income that we can put into bitcoin and then therefore how much bitcoin we might speculate that we are able to accumulate through our various accumulation strategies.
In addition, the presumably possibility that price will drop is a 50/50 chance but however, focusing on price drop to accumulate is basically if not the same thing with wasting to try to find the best entry point. hence it's more of a better opinion to figure out how much you're willing to sacrifice for bitcoin within your discretionary income. if we have enough it's even more advisable to buy aggressively as long as we can afford it without tempering with our daily expenses which will lead to deeping hands into our investments.
It all goes back to the initial planning that we have determined so regardless of the price of Bitcoin, if it is time for us to add assets then it must be done, it is a DCA method and I think it must be done consistently.
Regarding the possibility of the price of Bitcoin to fall, of course there is still an example, today the price of Bitcoin experienced a correction even though it was not that deep, but the market moved quite fluctuatively so that everything could happen in a short time.
If you plan to add Bitcoin assets and invest long term, I also don't think about spending a lot of time waiting for the right time because overall for the long term I am still quite sure that the price of Bitcoin will continue to rise and that is what we have been going through for the past few years.