Just chiming in with some more details.
What version of Gems of War will the Switch launch with?
The Switch version will launch as the 4.2 update. Unfortunately we couldn’t get the 4.2.5 update in the launch version with the important Hero Class changes. However, for the first update we’re planning to synchronise the Client versions, which will include the 4.2.5 and the 4.3 patch at least.
Keyboard and Mouse support?
It’s not something we’re officially supporting at launch, as it hasn’t been tested. We may look at official support down the track.
Day’s notice before official launch of the game?
If the release date changes, I believe it will also update in the eShop.