Let's make something clear here. Staal can visit as many doctors and specialists as he wants, but Marc Staal is going to be the one who ultimately decides when he can play again. Concussions are a very tricky situation, and every single one of them is experienced differently.
Staal is the only one who knows how bad the headaches are (they're improving) and, like Sidney Crosby's situation, he needs to be the one who gives the OK. If rushed back he could have his career ruined like Marc Savard, but if handled properly he can be back to his normal level of play when he returns.
For now, it's getting better. It might be slow progress, but it's better than no progress at all.