I wonder how many areas there'll be in the final game if the max lvl will indeed be 12/14, since lvl 6 is be pretty attainable by the EAs' end. Maybe they just sped up xp gains for right now.
I don't see any reason why Larian wouldn't be willing to do a sequel linked to the original story and a higher starting level unless they feel it would make for a difficult entry-point for new players.
I feel like they would most assuredly feel that way. Nowadays everyone tries to make sequels super-accessible to new players, and throwing them into a lvl 12 character with all the abilities/passives that come with that is pretty against that.