Not worried.
He's guaranteed a roster spot, which is separate from playing time. There is still a lot of skill there that one can not teach.
As for the scrimmage performance, it would be interesting to see him get time against Czuczman and Lepkowski and Gauthier-Leduc and see what happens to his scoring totals. Everyone is going ape over the game Girgensons had and he (and everyone else) ate up an undrafted-invitee and two AHL-ish talents on Gold's defense.
I'm more worried about JGL at this point than any other prospect in the system. He appears to be another PP specialist who is not grasping the fundementals of sound d-zone play. When the thought was that he'd take a long, long time... well, he doesn't look much closer.
Hmm, seems to be some divergent opinions on here. I recall someone saying JGL was the best player on the ice at one point in Dev Camp. (I cannot recall if it was during the scrimmage or during one of the shinny days.)