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Physical version of Mario Kart World will cost €90
(hexbear.net)
And on the American website, the MSRP is $80, with no distinction made between digital and physical yet.
There will be lol. The Switch 2 is already confirmed to be backwards compatible (likely without dedicated hardware as it'll be the same CPU architecture) and with that implies a whole bunch of necessary work to get shit working will have been done already.
Whilst new projects will avoid existing code like the plague to avoid DMCAs, there will likely be some recurring contributors from those original projects that have the technical knowledge just like before.