I felt a little let down by the WiiU and had planned to wait to purchase the Switch. That changed when they released the BotW trailer. I immediately per-ordered it and a Switch so I have had mine since day 1. I don't think there is any way they have had time to make a new Zelda. I think Metroid is too niche for them to launch with one of those. Same with Splatoon4. That just leaves a Mario launch title, while Mario is good and I normally buy them it alone will not be enough for me to go after Switch 2 Day 1.
I will likely be an early adopter and I will buy new rather than used (I mostly buy Sony used since PS3 days). Who knows though maybe I will still buy day one to avoid scalpers because I'm sure one of my must have franchises will be out in the launch window if not perhaps at launch.
All that said I am ready for Metroid, Splatoon, and Zelda and am quite ready for the Switch 2.