Honestly, very few people will enter Mouse Gear in the first couple of hours. Mostly those who forgot something essential (sunscreen, autograph book, etc.) or if a special item has been released, but you wouldn't see it pick up until around lunch time. And although the store won't open with the park, there are still many CM working at that time (and have already been there for several hours). The vast majority of early arriving guests are running to the attractions or character meals.
It doesn't sound like its closing any earlier than normal though. If I recall correctly, the official word is already "park close" but the store stays open far longer than that. Unless they're doing an absolute hard close every night, which sounds like madness, I only see this as a reduction of the least busy hour of operation. I don't believe it's as huge a deal as people are making it out to be - at least, for now. Who knows what the future will bring.