As I've felt for a long time now, I think Nintendo has been heading for a specific universal design for more years than we realized.
Gameboy and Gameboy Advanced games could be played on the GameCube with the adapter. The Advances could even function as a GameCube controller via Zelda: 4 Swords Adventure.
Wii's lack of graphical advancement allowed DS to play catch-up for a generation and get their teams further ready years ahead of time to unify.
Wii U was a massive leap forward in graphics over Wii, but 3DS was a pretty significant one over DS as well. Now both teams were fully developing 3D games (not the gimmick kind), further preparing them for unity. Also, there were similarities in design and function of the systems now as well such as friend codes, Mii's, eShop, etc.
Now they have unified divisions for hardware and software. Looking at the past and the success of the launch of Switch, I'm further convinced they will not leave this unified, take it with you or blow it up on the big screen mindset going forward. The only question is what it will look like in the future.
For the next generation (probably launching anywhere from 2023 to 2025), I don't think my more radical prediction will be doable in a typical Nintendo cost range they expect consumers to buy ($350 or less). For Switch 2 I expect them to make a skinnier device with multitouch technology, 1080p screen, gen 2 joycons with no drift and more features, Bluetooth, maybe bring back 3D without glasses again or something like that, and pack it with a dock that can run something beyond 1080p but probably not 4k.
It's Switch 3 that excites me the most though, and the future that could follow after. We are heading to a hardware-less future for home gaming, but to game on the go you will need something. No one takes or will take a PS4/5 or Xbox into a public bathroom while waiting to board a train. A switch? Heck yes! But what about home? I predict by this time, with a simple swipe of the finger while playing on a Switch, you will be able to swipe the game on to your TV without a dock, completely powered by the Switch that you set down, all in 4k. It will stream to whichever screen you want to in your home, your friends home, the local Best Buy so you can see what the TV will look like playing your favorite game, public TV areas even, wifi bars, coffee shops, etc. You won't just be able to game on the go in the palm of your hands, but will be able to put your game and skills on display for any you wish to do so in front of. then, when someone else wants a turn, you swipe down on your screen back to your portable Switch and let them swipe up. You won't even need the internet, and you'll be able to utilize any screen you wish even if there is no internet because it will all be powered by a local cloud called the Switch.
This is the hypothetical future that excites me. REALLY looking forward to 2030 and beyond.