They're probably wanting to jump forward to a place in time where they think they can better work into the show. They've made similar jumps before in their timeline. They can cut out a lot of fat by jumping ahead 6 months. They can advance JJ as far along as they want in the space program without actually showing what may be boring progression. Meg will have already witnessed alot in California, and may be getting homesick. Classes may be starting up for Beth in the New Year. It will be interesting to see how they will explain plopping Roxanne into a role as Bandstand Hairdresser. I also wonder what will have come of Uncle Pete and Chris' Mom (Shelly?).
I think, the jump is probably designed to align the show with cretain historical events. As for which events, I am not prepared to hazzard a guess!