Retirement age will increase, we will have to bet on robots to become caregivers or else there will not be enough able bodied people to do so. There will be lesser and lesser young people globally. And Africa seems to be getting a larger pie of the total population of the world.
So how does this impact Buddhism into the future?
Given that total percentage of Buddhism is still a small fraction of the world, it might not have too much of an impact as we can imagine Buddhism to be like a country. The amount of people who converted later in life is similar to immigration into the Buddhism nation. The amount of Buddhist parents who successfully raise their kids as Buddhist and stay a Buddhist is our birth rate and the amount of those who leave the religion is the immigration out of the nation.
The total number seems to be remaining almost the same until 2050, then perhaps eventually like the global population collapsing, total number of Buddhists might collapse.
A key factor to see growth is the conversion of the growing conversion of Africans into Buddhism, whereby investment into cultivating African monks, training them, helping them to establish a monastery in their home continent, and providing the expertise, translations etc would mark a great investment into growing the total number of Buddhists into the future.
In terms of amount of young people who could become monks, if Buddhism manage to continue to spread amongst young people, and only a certain percentage of them would be willing to become monks, it highly depends on whether the global population decrease of young people is faster or the conversion of them is faster. With less young monks, we might be seeing less senior monks into the future who are multi talented in academics, meditation and so on, and thus a weaker Saáč gha in general.
As retirement age increases around the world, those who would wish to become monastics when they retire would really be at even a greater disadvantage as they would have less time for their own self practice. If they are wise, they should quit immediately and just become a monastic, instead of trying to save up money for family, when universal basic income is likely the global solution for AI induced poverty. But still, since itâs not for certain that this future would happen yet, itâs understandable why people would prefer to continue working.
As countries like China, South Korean, Japan, etc continue to shrink in total population size and immigration would be very difficult due to language and cultural barrier, there will be many temples, monasteries etc, which will become empty and abandoned. Should any monastics already having the language requirement, it might be a prime real estate to take over those abandoned monasteries. But then one would lack the devotees to serve to as well. Whereas other places like in Africa, they would need fundings to build their monasteries. So nations which can produce a lot of monks might want to consider training their monks in languages of the countries which they are likely to be sent to for ease of delivering dhamma talks in the local language.
English Buddhism by no means is a saturated market yet, but in general most developed countries are at below replacement level fertility rate, and one might be well advised to focus on countries still with above replacement level fertility rate for best return on investment.
Of course, all are deserving of the treasure of the Buddhaâs Dhamma. In the short term, it seems that there will still be more younger monks compared to older ones, but when those young monks become old, it might be much harder to get young people to become monastics, especially when Africaâs birth rate would go below replacement levels as well. Then by that time, the only way Buddhism could continue as before is to increase total number of Buddhist as percentage of the worldâs population, which seems unlikely for now. And even if 100% of the world became Buddhists, the world population would still shrink. And we would eventually have lesser and lesser lay people to support lesser and lesser monastics. Who knows, maybe humanity would go extinct this way or maybe after Universal Basic income, nuclear dismantling, world unification, carbon removal from the atmosphere, global healing, everyone going vegan, birth rate might grow back to replacement level. Or we become pseudo immortals, to live as long as earth or the universe allows us to live.
Yes, Most people cling to existence and want to live forever. How do u sell what would look like permanent suicide to them 
I actually edited/ added what Iâm seeing from the other side as an after thought, but yes Iâll make a post about it tonight.
May you find Enlightenment soon, so that all beings may all be happy.
