I think the disastrous launch of the Wii U has to be a reason. By now Nintendo has realized that since they have no competition, they don't have to rush their hardware.
This is exactly why I don't think it's coming this year. System's still selling really well, software sales are still obscene. Why disturb that?
This idea is one that needs to die. Companies release successors to still selling product lines all the time. This is fundamentally how the Game Industry itself has worked for decades. The Switch is a household name at this point, same as Playstation and iPhone. People will buy a new one just because its a Switch 2. The brand has established itself.
The hard part is over. Releasing a successor is the easy part, now that people know what the Switch is and how it works. Nobody's going to be guessing or wondering about what it is. I have a little cousin (just entered high school this year) who owns a Switch. Its broken, but he's yet to buy a new one specifically because he's heard rumors of a successor coming out. Normies will sit up and take notice once they see a new thing,
because its the new thing. Now's the perfect time to launch because Sony and Microsoft are at least a few years out from releasing successors to their own systems, despite their lack of sales. Nintendo will basically have a captive audience looking for something new.
Yeah bro because Switch leaks are so reliable.
The last leaks released real information, were reported by reliable sources, and carried in major news outlets. These weren't some random hobos on Twitter. Once more, there is all kinds of confirmed information that we know that indicates that the Switch 2 is coming out soon, such as all the leaks that came out of the Microsoft Activision buyout trial, and confirmed reports that Nintendo is already showing off target hardware to third parties.
Steam Deck is good but isn't going to influence Nintendo's decisions beyond perhaps (hopefully) considering it to be the minimum specs for Switch 2 to target. Nintendo will probably include a new gimmick, but it'll be something unobtrusive and secondary.
I can't see Nintendo adding a new gimmick. There's no point. The Switch design has shown itself to be solid enough on its own, and Nintendo has already been stung by bad unnecessary gimmicks before. If its not broke, why try to fix it? Which, of course this being Nintendo, trying to fix what isn't broken is exactly what they will try to do because doing the least logical thing in any given situation seems to be their MO.
If games on Switch work with its successor, what reason is there for develop games targeting the new platform if they work just fine on Switch? You can already see this effect on PS4/PS5 where a LOT of Japanese games just release on PS4 and say who needs a PS5 version? And then there's even fewer reasons to get a "Super Switch U2 360" if there's still a ton of Switch games coming out.
Your assuming a lot, like that any game made for a Switch 2 would work for a Switch 1, which is just not necessarily the case. Many Japanese games are releasing on the PS4 because:
1) The PS5 sold like shit in Japan, so the PS4 still has the larger install base.
2) Sony themselves have muddied the issue by continuing to support the PS4, mostly because the install base for the PS5 is next to nonexistent, largely due to the fact that Sony struggled to even stock things for years due to supply chain issues caused by COVID, combined with over aggressive scalpers. Add to the fact that Sony's own first party output has slowed down tremendously, meaning that they simply can't put out big games in a consistent manner due to cost and development time, coupled with the falling quality of their own game releases, and Sony pushing PC publishing, and you've got a recipe for disaster. Fact is, the PS5 has no games, and Sony not simply dropping the PS4, once again due to supply issues, is part of the reason for that.
3) Finally, you are right that there isn't a massive difference graphically between generations. This is, to paraphrase Raz0rFist "This consoles are not designed to be powerful, but to be CHEAP", as in cheap to produce. Sony aren't pushing a massive leap in technology between the two. There is a difference, but Sony have undermined the difference by continuing to support the PS4, pushing the idea that its "good enough".
That last part I want to harp on because it goes back to the tech argument you alluded to. The situation between the Switch and the Switch 2 would be
completely different that the situation between the PS4 and PS5. The Switch is seven years old. Its an aging piece of hardware. Even when it released, it wasn't the most powerful piece of tech around and was well behind the competition. Remember, cheap, not powerful. This has massively effected what Nintendo are able to do with the Switch, but much more so what third parties are able to do. Many key third party games have simply skipped the Switch entirely (Red Dead Redemption 2, Elden Ring, Ace Combat, Tekken, Soul Calibur, Yakuza, Armored Core, Baldur's Gate, etc.) simply because there was no way it could handle them. The few that do make it to the system (like The Witcher 3, or the ports of the newer Resident Evil games) don't look good or run particularly well, due to the console's limitations, especially in handheld mode. Some games (ahem, Resident Evil) had to be cloud based. When it comes to indie games, the Switch is second to none. When it comes to major third party releases, the Switch either gets delayed, downgraded ports, if it gets ports at all, or ports of games that are, sometimes, years or even decades old. However, there has been massive jumps in mobile technology since the Switch launched (see the Steam Deck) and Nintendo are primed and ready to take advantage of that. It would at least make the console capable of handling major third party games, and put it on more (not directly) equal footing with its competitors. There won't be a small jump between the Switch and its successor, there will be a
massive one (comparatively). You see mobile technology, unlike PC technology, still has a long way to go, and Nintendo can take advantage of that to easily iterate on their consoles. As of now, if you want a full gaming experience, the Switch can't be your only gaming device (a common refrain is that if you get a Switch and a gaming PC, you can have access to entire breadth of gaming). With the Switch 2, that may actually be possible.