a short announcement to launch timeframe is the best thing Nintendo could do.
just have a big reveal in January where they show all the improvements to the concept like the new joycon mechanism. show maybe a tech demo to show people that the system can run current gen ports, and then reveal Super Mario 128, or whatever it will be called, as a launch game. (naming it Super Mario 128 would maybe be a genius PR move tho...)
hype up Switch 1 owners by showing free updates for their favourite games, like Zelda BotW and TotK running at 4K 60fps, Luigi's Mansion 3 running at 60fps at higher res etc.
and then present the first party lineup for the first year. where Metroid Prime 4 launches as a cross gen game that has raytraced reflections on Switch 2 or something... announce Mario Kart 9, some new whacky IP, maybe a new IP with a more serious/mature tone.
and finally a trailer reel for 3rd party ports like Cyberpunk, Fortnite, Space Marine 2... stuff like that.
the only thing that really can go wrong here is if Nintendo doesn't have a strong software lineup planned... but the 3 month reveal to launch thing is not an issue, and also not unrealistic