However, if we look at year 2100 then it seems rather clear that a majority of population will not ever be able to make any real contribution to wider society whatsoever, since any job that they can do can be done better and cheaper by someone else (machines or other people - e.g. being a third rate guitarist is of no use if you have many first rate guitarists that also are eager to work for free) so there can be no practical, economic reason to ever choose them for any job.
Subsidizing people who aren't contributing to society seems the only humane option. Having them "contribute" to society in some artificial way is not a solution, since that policy by itself would be a net negative to society; Not subsidizing them is not a stable solution, since in the absence of any reasonable ways to survive they'll either starve to death or manage to violently overthrow the system.
In essence, the likely future involves the unprecedented scenario of billions of people who are, from an economic standpoint, absolutely unnecessary and a net economic negative to society; and the only (?) possible solutions seem to be either to accept that we'll subsidize them or exterminate them. Or, possibly, "others" will subsidize or exterminate us, as it's not set in stone on which side I or my kids will be.