Well when I first saw the thread title my immediate reaction was "No, that would be stupid, didn't work the first time, would be worse now."
But, talking just about box sets. I do believe their will be more box sets. And I think those are good things. But, using them as a means to expand upon the rules is a *bad* thing. I do note that they have effectively done that with sidekicks, and I'm not sure how that is going to work into the mainstream.
Using SKs as an example, I'm not a person who will probably ever buy Essentials for myself, so how do I incorporate or get the SK rules to use? Other new rules will just make that problem even worse. They have a strong model now with the large AP books that add new and appropriate rules people know where to go to get the new rules. And their is very little rules (or content) overlap.
Hence if I buy a book, I know its' not going to overlap with other sources. The boxes don't do that. They duplicate existing rules, and provide a nice box with all the trinkets that are fun to play with. I hope they continue along those lines.
I like the idea of an Explorer's box. It could include the rules for gnomes, rangers and druids. Include a nice hex crawl map and include the sections of the DMG for such exploration. And of course include a bunch of beasts from the MM and other sources. Maybe it might even include a remake of Expedition to Barrier Peaks...
A Seafarer's box could include a map of the MoonSea, and punch out cardboard 3D ship. Include any rules expansions from Saltmarsh (haven't looked at it yet, but people talk about ship rules). Don't know what races and classes you would include, would have to look at what's in the other boxes. Maybe just rules for levels 6-10 or so.