I think the only logical form of the "hybrid but no Joy-cons" prediction is one where it's not actually a hybrid, it's another addition to the the current plague of Steam Decks and Steam Deck ripoffs, which are purely handhelds, with TV output and external controllers supported only as awkward optional features that most people won't use.
That would be garbage, since the handheld PCs are a strictly worse hardware proposition than the Switch is today, and I have no idea why anyone would think Nintendo would do it, but at least it makes sense as a concept. I haven't seen anyone coming out and saying that though, instead it's being framed as, "what if it's still like the Switch, just without Joy-cons (somehow, even though that's impossible)."