I really, really love the switch and Nintendo games. I just don't think I'll ever have faith in Nintendo being capable of doing online properly. So I want someone else to make another handheld. Heck, if Sony won't do it, I wouldn't mind an xbox portable. MS has been so good with backwards compatibility, letting me play and keep my old purchases.
Sadly, it was rumored ages ago that MS wanted to step in to the arena, but that was also when mobile was clearly starting to cut in to most gaming, especially the portable market. I think they just saw where things where headed, and knew it wouldn't end well, so they didn't bother. Hell, they have no clue with the ONE currently, so I don't think a mobile device may have done any better. The best you can do now is something like the GPD Win 2, that allows for pretty much PC level gaming on the go. The cost of that is thru the roof, so really not a cheap option, but a pretty cool one if you have the extra funds.
As for another dedicated portable from anyplace, that will have to fall to "N" sadly, as they have been successful in this arena since the start, and have sent each competitor crying to their graves. LOL There was always a better handheld along side "N" offerings(hardware wise), but the combination of price, kid friendliness, battery life, etc always gave them the clear win. The DS was the tops of those efforts before mobile totally eroded the market, as the 3DS sold maybe half of the DS numbers give or take(I'm not exact on figures). This most certainly led to the NS, as "N" had no hopes of competing in an heads up console battle, so they did what they do best, and added their portable successes with their often failing consoles, and well......you know the rest.
After the 2DS/3DS have stopped bringing in the budget friendly dollars, I'm certain they will offer a more budget friendly NS(switchless, mini, NS Lite,etc). By then the tech in the NS will be dirt cheap, and they should also have a much better library by then, which would make a sub $200 device for them key to long term success. But outside of something like that, I don't see anyone else coming out with anything that could even come close to what the Vita or the 3DS has been. I would love to be proven wrong, as portable gaming is 90% of my gaming, but like all good things, stuff comes to an end(and we have to live with it).