I think Beach will be an NHLer, but will always be a disappointment.
I think Beach becoming an NHL would be a great surprise judging by most the posts in this thread.
If you expect him to be a top 6 power forward you will likely be disappointed. If you are judging him based on his draft position and supposed potential at the time, yes he will likely be a disappointment.
But expectations and "potential" change from year to year. In one year Nick Ebert went from an expected top 5, with top 2 potential. The next year he was drafted in the last round with the last pick. Expectations and realistic potential change from year to year. It happens to every player as they get older and as they get scouted more and more. Ludvig Rensfeldt was drafted 35th overall with top 6 potential and 2 years later Stan didn't even sign him to a contract.
You can't keep the same expectations for players 5 years after their draft. It changes. If you would've asked Erik Karlsson's top potential 3 years ago it would be less than the player he already is as a 22 year old. You are setting yourself up to be disappointed if you expect a 30 goal power forward.
However, that doesn't make him useless like some like to spout off about. Stan didn't sign #35 overall Ludvig Rensfeldt just 2 years after he was drafted. Stan traded 2009 1st rounder Phillippe Paradis. Stan traded 4th overall pick Cam Barker away(granted for a great return). Obviously Stan or someone else high up thinks Beach can be an NHLer contributor or he would've been moved(like Skille) or unsigned. Some people here who don't watch any games think he will never be an NHL talent but ill side with Stan and their scouting/management team. He wouldn't have kept him if he thought otherwise.
I'll be disappointed if Beach never becomes a full time NHL regular. BWC will be disappointed if he does become a full time NHLer. Everyone has their own opinions and expectations and at the moment I don't think they are very high as a whole.
So I agree that he is likely a disappointment relative to his draft position but many of us have moved past that draft 5 years ago and have more realistic expectations which may or may not end up in disappointment.