If i had to gues why are we limited to lvl 4 ... there are two aspects:
Early Aces aspect: At first at least i dare to say that since we dont even have all spells for levels 1-4 ... (for example ... shield) So ... i dare to say that they probably didnt have level 5 even prepared for us.
Full Game aspect: While for level 4 some fights are really hard (but not impossible, sorry) ... Many combats would be ridiculously trivial for level 5 ... As it was few times mentioned around here ... party with two, or three casters able to use Fireball, would probably be able to obliterate whole Goblin Camp within single round.
But its true that level 5 is one of bigest requests from comunity and even Swen in penultimate(?) Panel From Hell litteraly said that talking about level 5 started. Not sure how he meaned it tho ... the exact words were "The jury is still out on that wheter or not we're gonna put level 5 in Act 1 so if you keep asking hard enough maybe one day that is going to happen." Notice that he dont say "early acess" but "Act 1".
(time: 2:09:55)
I still dont understand why cant we change Race for our hirelings. Lets us play Githyanki as racist as they trully are!