Probably none of those, too many of those would break backwards compatibility within the system and for as awful as some of Nintendo's moves have been they have thus far not gone there. Closest you really have is the wii without GC ports possibly blocking some stuff (though technically all games should have had wii functions, I agree though lack of GC controllers in some games is fatal for my enjoyment), and the DSi breaking guitar hero by not having the controller and arkanoid would not have the paddle control either.
So yeah joycons are probably here to stay, outside chance that it internalises some controls and allows you to use externals for those games that need it.
TV. There are touchscreen only games either happening or in the works, said same discussions appeared to hint that docked only would not happen. I know the PSTV happened but even on the vita scale it was a failure and ended up mostly getting sold off cheap.
Switch XL I can see happening at some point but probably not in the way you think, 7 inches is the point at which screens start getting odd and the current one is 6.2-inches apparently. Likewise even if the power and heat issues could be sorted I am not sure there is a massive case for 1080p in handheld form and likely not for the already tech shy Nintendo. If it happens I would probably imagine it happens as a result of 1080p panels becoming the only viable option on the market, and I don't really see that happening too soon as industrial uses will probably keep bright small touch panels being pumped out in lower resolutions for years to come.
I would like to see microHDMI or something appear but all the warranty claims that would result is probably enough to give pause; I can't be bothered to look up the plug-unplug ratings for a microHDMI but I can safely say if you thought dodgy charge ports on phones was bad you have seen nothing yet. I would bet on a micro dock or dock redesign to make it more portable before that happens too.
Said no docked only games probably means no performance expansion dock. If they get desperate then maybe but they already have one of the most powerful phone/tablet class devices on the market, and I doubt a dock is going to make COD, full fat fifa and battlefield suddenly appear.
I imagine most of the earlier hardware tweaks will be towards battery life, getting that heat down and maybe a better dock. I might like to see backwards compat with the 3ds but I doubt there is a big enough draw for it (3ds has no games), and if push comes to shove you might just about be able to do it in software.
"introducing the switch S, it is the same switch you love but now lighter, with a brighter screen, more battery life and comes in 4 new colours (or three new colours that can be selected in the plastics factory and a cheap decal as it is [insert Nintendo property]'s anniversary/time to be brought out to see if we really can sell old rope".