When the Parks Blog announced it, I think it was more or less a surprise to all of us. I don't think anyone had heard of a Beach Side Bonfire Buffet in the works before it was revealed.
There doesn't seem to be any end date for this buffet so, while the theme of it sort of seems summer-specific, since it also fits with the general theme of the hotel and the PCH Grill in general I think it will probably stick around for a while. Maybe a few of the buffet items will be switched out here and there as seasons change, but if it continues to be popular enough it will probably be there for the foreseeable future.
I think it was a good idea to put something new and theme-specific into the PCH Grill. Anyone who has ever stayed at the PPH may have noticed, when walking from the PPH to the GCH or from the GCH to the PPH, that the PCH Grill was often nearly empty at night. Even the Surf's Up character meal doesn't really pull in the same kinds of business that the other character meals do. They needed to freshen things up and do something to get people to walk over there for dinner.