I wonder if they will. I can't imagine anything trackpoint-like -- too expensive -- but it's not impossible they'll put a trackpad in.

The Pi 400 is small because it's meant to be aimed at the young. But young children are good with clicking buttons and poor with fine dexterity; they will likely do better with mice.

A clip-on trackpad to go alongside it would be nice, though.

I'm not really the target market but I am hoping a Pi 500 will tick all the right boxes to use as a cheap computer in a space-constrained workshop.

Please don't, that's added cost that 90% of us don't need.

If you're trying to minimize cost, get a pi board and add your own keyboard, instead of getting a 400/500. You need a pointing device anyway so it's likely to be cheaper to have it built in.