6 year terms just might be a little too much for a goalie. Every team comes to regret them eventually.
My thinking is IF the team is playoff ready and Ullmark is the reason then you give him the bigger deal at that time.
If he would sign for 4 or 5 years at 4 mil per maybe that could work but I would think he and the team would appreciate the flexibility of a two year deal so they can see what happens going forward.
If the team is still struggling, he or the team can move on at that point. He'll still young enough to land another good deal.