I thought about that a lot, and I think that increasing the level cap to 5 in EA would be really helpful for everyone.
Problem as I see it now is that EA has enough content in patch 5 already to even allow for level 6 (level 5 is reached quite some time before the content ends, lots of fights after that, etc...).
And then also this would allow for trying out the balancing at the (actually gamechanging) level 5 and beyond. We will not know, just to give an example, how "Fireball" will play out.
Another reason is that I think that quite a few people would love to start over if level 5 is added, but with the level still capped to 4 I don't feel like doing it, just again.
Horizontal (more classes) vs. vertical (more levels) progress should be balanced.