As stated, level 11 through 13 is the most likely range, allowing for a peak at level 6/7 spells and similar upper mid level melee attacks and skills, and at least two huge leaps in character mechanics. Once you get past that, you are working with high end characters approaching, if not at, epic levels.
That would require another quantum leap in development, programming, imaging and writing - while foreclosing any meaningful sequel.
If you are looking for a D & D game with that range - level 1 through 14 - 20, Pathfinder is your best bet. It will be an awesome game, but less demanding in terms of cut scenes, and other areas higher in developmental costs/requirements.
I'm looking forward to the different RP experiences that will be available between Solasta, Pathfinder and BG3 - along with a few other such games coming out in the next couple of years.
This is looking to be a banner period of Fantasy RPG's.
One thing I realized I'd like to see is a series of games that are very class focused.
There's a benefit to a tight focus (one of the reasons I'm sort of on terminator's side that level 8-10 with a planned sequel would be better than just straight level 13/14 or all the way to 20 like NWN2) in a video game.
And I'm kinda curious how you could have a game that focuses on the story of the different classes.
Like really get into the meat of a warlock's story and their interactions with a patron.
It feels like you could get some really high replayability and extremely different story-arcs with each replay based on choosing different things for your character.
An overarcing situation independent of your character maybe but with beginning and end more shaped by your background choices than anything. Have the myth-arc be more background than center story... and the climax be personal.
Like a Fighter with a Folk Hero background culminating in a climatic battle with some corrupt noble or something. While a Fighter with the soldier background coming to a climatic moment with a jealous commander/comrade turned traitor.
Heck, if it were a series you could even have the myth arc be something unified between all of the stories.
Say a flood of gnolls, serious enough to spark demonic intrusions and various factions dealing with/responding/taking advantage of it. The world-threat is just the unifier between the series and the main arc is your character's personal story and it's geared toward your character build.
A good way to play with stretching interpretations too. A barbarian sage whose rage is less anger and more adrenaline fueled mathematical applications or maybe a it's a mystical battle trance type thing... but still be possible to play the stereotypical rage monster.