Look... Pelosi has shown no sign of losing a step (for better or for worse...) and is one of the few politicians that I believe would know if they are "up to it" or not. And she has a LOT of institutional knowledge.
But also? The Feinstein and mcconnel optics are already HORRIBLE. And she has already groomed Hakeem Jeffries who, hard-on for israel aside, is pretty awesome. Pelosi's seat is not at risk of being lost to republicans and she would be a lot better suited toward helping and mentoring people as an adviser, rather than being an active politician.
To your first paragraph, decline often comes suddenly. Of course with a two year term, and hundreds of representatives, it's not as critical of a risk as a 6 year senator, but still.