Splatoon 3 only has content updates for 2 years, same as Splatoon 2. They said that already, I would be very surprised if Splat4 isn't out by mid-2025.
That's the thing, I'm not expecting many major titles to launch with the system, at least not Mario/Zelda. It's practically confirmed Switch purchases are carried over, I expect them to emphasize hard on existing titles (Nintendo and third-party) at higher resolutions/framerates for the first year.
Actually, Mario Kart 9 is a pretty safe guess. MK8D was the best-selling game for a long time, easy money.
But again, why would they double-dip in Splatoon after how massive New Horizons was? 32.5% of ACNH's staff worked on Splatoon 3. It's not the majority, but it's also not insignificant (especially compared to EPD games from different divisions). If anything, Splatoon could use a little bit of a break.
As for your other point, Furukawa usually plays things safe. And given one of the sided reasons for the internal delay was to buy more time for first party games to be made, he likely trying to replicate the Switch 1's first year in terms of a steady stream of software. One of the big things that helped was a major release on Day 1, & 3D Mario would fit the bill.
Prime fans are the kind of hardcore players who either 1) will pick up a new console day 1 or 2) will pick up said console if it means playing Prime.
Install base isn't the end-all-be-all regardless. The Switch bump kicked in LONG before the Switch was at 9-digits, while Prime was doing the same numbers on the Wii's 100 million as it was on the GCN's 25.
Not really? Metroid is the kind of game you'd buy because you already have a system, not the other way around. As I mentioned earlier, it's becoming apparent that the goal is to replicate the Switch 1's success as much as possible. They need a heavy hitter on Day 1 for that to happen, something that appeals to all audiences (mainstream & hardcore). Not only does Metroid only really cater to the hardcore, it specifically caters to the
Western hardcore fans.
While I don't deny the possibility of a Switch 2 port, I'd put money on the Switch 1 version coming out. The last time Nintendo went back on the word regarding platforms was Super Paper Mario (GCN -> Wii), which was a long time ago.
It it doesn't launch with ARMS 2 I'm going to riot.
Gotta wait for the bigger EPD 9 seller (Mario Kart 10) to drop first. But given Studio 2's history of assisting with EPD 9 projects, their "3D action game" could very well be ARMS 2 (seeing as Studio S's "side-view action game" is likely Smash 6 considering their track record).