There's more to it than just available capital though.

A still-shrinking working-age population will have to look after a still-expanding retired population.

IIRC (no reference), Japanese pensioners on aggregate have lots of savings. However, they will surely be competing with one another for services rendered by the shrinking labor pool, so one would expect the costs of those services to rise, negating the effect of having lots of savings.

I live in Japan now and, unsurprisingly, the retirement home business appears to be booming, especially in and around Tokyo. But even if there are lots of retirement homes, they will have to be staffed. By robots perhaps?

Hopefully they'll relax immigration requirements? Maybe from Southeast Asia and the Phillipines? They're very used to working in the hospitality industry, a lot of cruise staff are Filipinos for example.

Yeah, I agree. Robots for sure. If the cost of developing an AI that can do this is less than the cost of hiring scarce labor... in 2050? Sounds almost obvious now that you say it.

>How is it different to have revenue going to services retirees need instead of going to new sports cars of big tvs

For one, the people buying those sports cars and big tvs are productive citizens and have decades of work and payments ahead of them...