|Pyro as Bill said:
Higher price - prices can be dropped.
Cazulaz went to smartphones - Brain Training and Nintendogs might be possible on smartphones but Ring Fit Adventure and Switch Sports aren't.
Cannibalising successor - I don't see it. All I see is a delay in upgrading. For some reason the hardcorez are already clamouring for Mario Kart 8 and NSMBUD in 4K just like when they wanted MKWii and Wii Sports in HD. It's great when people are dying for your next product 7 years before it even releases but I think Nintendo would be stupid to make MK9 and NNSMB exclusive to Switch 2. If the hardcorez want them in 4K, fine, but there's no reason why Switch's life has to be cut short instead of releasing them alongside a 1080p version for the original.
TL:DR - It's a portable PS3/360. The amount of life left in this BEAST is unprecedented. No offense but the PC, PS4 and XB1 brought nothing new this gen that wasn't possible on smartphones (in terms of success as opposed to VR). If Switch can run Fortnite, Minecraft, CoD, GTA5 and FIFA then Nintendo can keep it alive for 20 years if they wanted to. In terms of gameplay, is there anything that a Switch successor could do for Pokemon, SMB, Mario Kart, Wii Sports and Brawl that the original can't?
Yes it can run GTA 5 and COD but neither of these publishers want to release these games on it so...