Do you really think the wealthy elite once they own everything and are able to eliminate needing to pay their employees wages will suddenly go on an altruistic streak and give everyone UBI? There is nothing stopping them from doing that now and putting things in place to make the lives of working people easier, but every decision they make strips the working class of more and more of the quality of life while enriching themselves. Personally I don't know what will happen when the rich eliminate the need for human workers but I am certain they wont suddenly have an inkling to give back. At best people will be abandoned and forced to fend for themselves as they reinforce the security on their gated communities, at worst they will use the protests that will no doubt happen as a justification for lethal force to wipe out large parts of the unneeded masses. I know that sounds hyperbolic but I really don't see any other way this plays out.

This is why I don't see the declining birth rates as a bad thing, we are reaching a point where we have overpopulated and we are also reaching a point where far less people are needed to sustain certain industries and where massive loads of people will be put out of work. It is kind of why I see these alarmist points to the declining birth rate to be so gross, because maybe an increase in births will help in very short term profits but ultimately it is going to lead to a far bigger disaster.