Comparing Divinity made by a small studio with behemoth like Skyrim is already a success for Larian IMO.
Game they made is really enjoyable. Atleast i have only enjoyed as much when i was playing Fallout 2, Fallout new vegas and X-com (yes, i consider Skyrim a bit inferior to D:os, because it was oversimplified).
And i think D:os will be still bought for a long time like any other good game.
They just need to finish expansion in time to get more attentoion on steam once more.