There's still a lot of uncertainty but right now I'd bet on it selling less since the Switch had so many things going for it such as the concept feeling fresh, being able to use the Wii U library to pad out the release schedule for the first few years and the pandemic giving a huge sales boost. There's also that Nintendo no longer has a complete monopoly on handheld gaming with the rise of PC handhelds and with there likely being an Xbox handheld happening gamers who prefer handheld gaming and/or love having a device that does that and TV/monitor gaming will have more options for that compared to most of the Switch's life.
The Switch 2 does also have things going for it though such as it being the successor to one of the most popular consoles ever and Nintendo being in the best position it's ever been in popularity wise with its IP's reaching new heights. The sequel to the Mario film releasing next year is a taste of what's to come since there's surely gonna be a bunch of other films and things like that during the life of the Switch 2 helping keep Nintendo's popularity sky high. There's also that its third party support should be significantly stronger with it being way better from the get go and it getting a lot more high profile big games like Hogwarts Legacy.
Cause of things like that it should still be a huge success so if I had to make a prediction right now I'd go with it selling 130-140m and taking the 4th place spot. It probably lasting at least a full 8 years like the Switch has will also help a lot with it selling that much. The biggest question mark is how successful the first party games will be since replicating the success of something like New Horizons won't exactly be easy. Ideally they'll blow people away with the April direct to help it have a strong start.