If they can get it smaller and lighter, I don't doubt that they will. My non-engineer/non-designer's mind can't think of anything that could be nixed with the upcoming model, but I've been surprised before.
I wouldn't be surprised to see some changes in the nearish future. I would bet they'll get rid of the optical drive once it's a little more practical to do so than it would be at present. Hard drives/SSDs can and will be made smaller than they are currently, and batteries/power usage will continue to get more efficient.
So, yeah, smaller and lighter will probably continue to be inevitable, but, of course, we'll only know for sure that it's coming when it's officially announced.