How much do I want to bet, or how much am I thinking?
Assuming it's the latter, look at the sales of the other games. Even the weakest entry did nearly 500K in Japan. I think that having gone a hiatus will eliminate some possible burnout, and with that combined with the overall success of the Switch and a relatively light release schedule atm, I'd be surprised if it does under 500K worldwide. As for 250K, it could probably hit that in its first month.
You might want to look at the series sales again
Blue/Red Rescue Team (2005)-1477k
Explorers of Time/Darkness (2007)-1552k
Explores of Sky (2009)-448k
Gates to Infinity (2012)-405k
Super Mystery Dungeon (2015)-296k
Switch boost only applies to the West where 3DS did mediocre, it doesn't apply to Japan where it is the 3rd best selling platform of all time.
You can see this by comparing Switch to 3DS entries like 2D Zelda, Fire Emblem, Kirby, Yoshi, Donkey Kong, Luigi's Mansion, etc.
I missed Super Mystery Dungeon. This site has it at 350, and gates to Infinity at 470. That site seems sketchy, or at least not updated often enough, because the numbers here from Famitsu are a lot higher than the numbers they're giving for Switch games.
Based on this week's numbers, Star Allies is ahead of Triple Deluxe, and is still in the top 30, so it will most likely outsell it comfortably.
Based on that site, Tropical Freeze and returns had nearly identical openings, and we don't yet know which will end up selling higher in the long run.
Super Mario Party is outselling the shit out of of either 3DS entry. Or both combined for that matter.
Mario Odyssey will almost certainly outsell 3D Land by a comfortable margin.
Mario Kart 8 is a lock to outsell MK7.
Smash Ultimate already outsold 3DS and will almost certainly outsell 3DS and U by a sizable margin.
Sonic and Mario looks likely to outsell the 3DS entries.
Captain Toad Switch has outsold 3DS.
Luigi's Mansion is way behind, but is still selling incredibly well, so we can't say which will sell better.
There's some variation on a game by game basis, because Link Between Worlds was just better than Link's awakening for example and Mario Party makes more sense on Switch, but overall it seems that software sales are better on the Switch from all of the examples I could think of. Still very much willing to bet that it will sell at least 250K.