The variance of answers in this thread illustrates exactly why games like this can never be "perfect". Everyone wants and expects different things so no one can truly be happy. Some think starting at lvl 1 sucks, others want to hit lvl 25, etc.. This is Larian's first D&D game and it's taking place 100 years after BG1/2, why in god's name would we start at anything but level 1? I get that some that play a lot of low level campaigns would like to play higher levels but a lot of people have never even tried D&D of any sort so starting off at higher levels makes zero sense from that perspective. New players should be introduced at low levels to grasp the mechanics and also experience the growth of the character properly. Starting off characters at level 3 and forcing sub-class choices before they even get a chance to understand what ground zero feels like doesn't make a lot of sense.
Level 10-12ish seems like a fine ending point for the standard campaign and if the game does as well as everyone is hoping I don't see how we wouldn't be getting some form of DLC to allow us to play even higher.