None of these are predictions. (We think anyone who has a confident multi-year interest rate forecast is deluding themselves).
But you are making a very bold prediction. You outline four scenarios and their impact on affordability, one where they stay the same and three more where they go up by varying amounts.
You all but rule out what I believe is quite likely, which is rates go down.
I also, for the reasons above, think you may be implicitly dismissing the chance of higher inflation with declining or flat rates.
While I think the low inflation and low rates is most likely, high inflation low rates is an easy enough scenario to imagine: BIB and BBB both pass, the boom continues, incomes rise and partly bleed into higher prices, but partly are saved. Dem gains in 2022 are unlikely but possible, and I think would lead to an even bigger round of BidenBux that again is split between consumption and debt reduction.