Sure it is a matter of time and also a matter of quantity, including front loading. A guy from 10 years ago could have bought $5 of bitcoin per week and invested $2,600 by now (over the past 10 years) and he would have accumulated more than 1 bitcoin.
From the article, the guy suggests $250 per week, yet I question if $250 per week would be enough to get to 1 BTC in 10 years.. and so if someone wants to assure to get to 1 bitcoin in 10 years, he probably needs to invest more than $250 per week.. perhaps more than $500 per week, and even that might not be enough. $500 per week would get right around $26k per year, which would be $260k over 10 years. Such a guy with $500 per week might be able to get to 1 BTC in 10 years or less. Perhaps? I would not have a lot of confidence that $250 per week would get a person to that level, yet at the same time, surely people have to work with what they got rather than fantasizing about what they do not have, in terms of discretionary income that they are able to invest in bitcoin in a sufficiently aggressive way, yet at the same time, without overdoing it and wrecking themselves in the process of trying to reach such a goal of getting to 1 BTC in 10 years.
I agree, these projections will all depend on the price of bitcoin in the next ten years and what it's yearly percentage increase will be, it could even get to having to invest $700-$800 every week with DCA be able to 1 bitcoin in 10 years, it could be more it could also be less but either way the chance of owning 1 bitcoin in the next 10 years would require an investor to spend more in the next 10 years through DCAing than they spent in the last 10 years through the same DCAing, there is no certain way to know for sure but with the kind of increase we have seen in the price over BTC over the last decade then it won't be far fetched to say owning 1 BTC over the next 10 years will be more difficult than it was in the last same 10 years.
So at the end of the day, it's only a matter of time and quantity.
With any work done diligently and consistently, I don't think it will be difficult for anyone to accumulate one Bitcoin for future investment. This is because it is highly influenced by a person's confidence in owning Bitcoin and never hesitating to continue buying without any reason. And if you're willing to dedicate ten or fifteen years to buying Bitcoin using the DCA method, you will have one Bitcoin, or even more. The DCA method isn't always measured by the amount of money you use each week to buy Bitcoin; you can use different amounts for each purchase in the coming weeks.
So, any investor who has started in the past few years and continues to use this method today will no longer be concerned about whether or not they can own a specific amount of Bitcoin. They will remain focused on their initial plan: to keep buying with the money they've set aside each week, so that the amount of Bitcoin they accumulate will continue to grow over time.
Growth in an investor's portfolio is certain as long as they keep investing in bitcoin, it might be faster for some than others but it will still happen, it will only take time, dedication and consistency on the part of the investor, over the course of a decade or two an investor's stash will eventually reach 1 BTC, so even though getting 1 BTC over the next decade will be harder now than it was over the last decade an investor will still hit that threshold if the are consistent enough in investing and HODLing for long enough