Today's big Super Mario 3D All-Stars announcement came with a few quiet limitations, the most significant being the pending disappearance of the game on March 31, 2021.
As Nintendo clarified in a press release, Super Mario 3D All-Stars will have a short-print physical edition and an impermanent digital edition. The "limited production" of hard copies will be available starting September 18, and the game will totally vanish from the eShop on March 31, 2021, after which point it won't be available for direct purchase. You'll still be able to play the game if you already own it, but if you don't buy it by March 31, you'll need to bite the bullet and hunt for a used physical edition at whatever the cost.
It's unclear why Nintendo has limited the game's availability in such a way, as the company didn't explain this narrow window in the announcement. Perhaps it's trying to concentrate sales in the next two quarters? March 31 lines up with the end of the fiscal year, after all. It's also possible that once the all-in-one trilogy is retired, the individual games will be available digitally from April 2021 onward. We've reached out for clarification and will update this story if we hear back.
It's also worth pointing out that Super Mario Galaxy 2, long believed (and rumored) to be part of Nintendo's Mario blowout, is not included in Super Mario 3D All-Stars. There's been no word of Galaxy 2 coming to Switch, and the game was conspicuously absent from the Super Mario recap in the big Mario 35 Direct. Nintendo may have Switch plans for the sequel yet, but it hasn't announced anything at this time.
Another minor caveat is tucked away in the official product page for the 3D trilogy: if you want to play Super Mario Galaxy in co-op on a Switch Lite, you'll need an extra set of Joy-Cons. This is standard for co-op on the Switch Lite, which was designed for one player and has its own baked-in controllers. Besides, the co-op mode just gives another player the chance to scoop up stars while player one controls Mario, so it's far from a deal-breaker.
Update - September 3: in a statement to Polygon, Nintendo clarified that Super Mario Galaxy in the Super Mario 3D All-Stars collection uses Joy-Con motion controls for the star pointer in docked mode. In handheld mode, which naturally includes the Switch Lite, the star pointer is controlled using the touch screen.