Where's the modular?

I have been DMing the playtest packets since the first release, and my group and I are having a blast. I have no real complaints. I find the rules very freeing and fun. Over all I think this is going to be a good edition.

The one thing I am disappointed with is that there seems to be no mechanism or design for the system to become modular.

Instead they seem to just be making a very vanilla and loose D&D system reminiscent of first edition without the murkiness. I am find with that. I think that is great, but I was very excited by the idea of there being a modular aspect.

I think being able to swap in different sub-sets of rules (maybe even from game to game or from encounter to encounter) would be great. 

It seems like this is being ignored. Perhaps I have missed some announcements or other discussions?

They're really trying to get the base rules settled before they deal with modules at all.  If you need an example for what they can do, though, look at the various healing options.  I really like the slow healing options, myself.

The metagame is not the game.

Yeah, as was stated before, we might be seeing such stuff laster on in other play-tests.  I imagine the goal is to iron out the core rules, have good balance between the classes while still having cool class abilities.  Keeping character race relevant.  Streamlining the rules, keeping the game moving, etc, etc.  I have to say, thus far in the material so far, the game 'feel' seems kind of like an "official retro-clone" of earlier editions of D&D.  I realize that what we're seeing in the play-tests are far from complete, I'm just sharing impressions of players in the testing I've run.  Have to say, I can't wait to see what's in store for the Ranger class... maybe next time...
[Firstly, see my signature.]

"Modularity" refers to all kinds of sizes of things, from Backgrounds and Specialties (a couple of large modules), to customizing ability scores (a relatively small module, more like a sidebar).

Some modules could take up a whole chapter of a book, if not a whole book (like tactical combat). Others may only require a paragraph or two to explain. A "module" is something that is not necessary to use to play the upcomng D&D edition, but can be added at each table's discretion.

Most of the modularity will exist as an expansion of the basic rules. But since the basic rules are still being finessed, modularity is a secondary concern. But we are seeing some of what it will look like now.
"Our idea of rules modules has a wide range of scope; sometimes, our rules modules might just be small tweaks and variant rules, while other times they could be large-scale changes and entirely new subsystems. We want people to make the game their own, and that means provided a whole array of possibilities based on what you, the players, tell us that you want." -D&DNext Q&A Blog, 8/29/12, Answer #3.