It's been announced that the final open playtest packet for D&D Next is soon to be released into the wild. After that happens, they're taking the rest of the design process in-house (or semi-in-house, since they'll still have a large stable of playtesters, just not an open playtest).
If the goal is to have a GenCon 2014 release, and everything I've seen thusfar indicates that it is (also coincident with the 40th anniversary of the game), they're actually not leaving themselves a whole lot of time to make additional changes beyond the September open playtest packet.
In order to have physical books ready for mid-August 2014, they need to have the final version of the book - text, art, layout, everything - completely buttoned down by the end of May. That will barely give them enough time to have them printed and shipped to distributors.
Now, assuming that they will need a month or two to get all that nailed down, including the final editing of the text, they need to have the *content* of the text done by March. (That's consistent with the time-frame they were working under for the 4E Players Handbook, by the way.)
Based on that, giving themselves six months to finish what they are calling "...the repetitive grind of balancing out the math and finding and dispelling abusive combinations" seems reasonable. But that's not basic design work. That's polishing.
Based on these factors, I think that the version of the game we get in the next playtest packet is going to be pretty close to the finished product. They simply don't have the time to make any more major revisions. Of course, the last packet was still missing what many gamers would consider some key elements, like multi-classing. One can only assume that the last open playtest packet is going to cover those sorts of things so they can get a broad read on how they're received. If not, it means they're putting them in the "balancing out the math" category, and I'm not sure that's a great idea.
All that said, I think what we get in the next and final playtest packet is going to be pretty close to the finished product. Not in every jot and tittle, of course, and possibly not complete, but close.