Elementary Content Specialists: Is it Time?

Over the last 10+ years, I've had the privilege of working with hundreds of K-5 teachers in math professional development. The longer I work, the more frequently a question comes to mind:

Is it time that elementary teachers specialize in subject content?

Why?

Sheer Amount of Content
New standards change and increase the amount of math and language arts standards that each grade level teacher must know. With new standards comes new curricula, hopefully of high quality (check yours on EdReports) and hopefully with plenty of supportive PD.

For some, new curricula (or good curricula!) is not purchased and teachers piece together their own. (For a recent statement on this trend, read a reflection by NCTM President, Matt Larson.) If one is to learn even one new set of content area standards--and a new, related curricula--it takes time to develop proficiency. Add in another major content area (or 2, 3, 4...) and you have a recipe for overwhelmed teachers.

Depth of Content
Over the last 10+ years, I watched many standards appear to come down a grade level (example: what was in 4th is now in 3rd.) Then it seemed to happen again. Much of what we learned when we were kids is now taught 1-2 grade levels earlier. I routinely work with 4th and 5th grade teachers to learn how to teach math content that they first encountered when they were in middle school. 

Please Note: I fully believe teachers capable of learning the mathematics. (See Jo Boaler's work.) But they don't always have the TIME to learn it.

Advantages
If K-5 elementary teachers specialized, they could focus, teaching one subject (or a major content subject and related subjects) twice a day. For example, a language arts specialist might team up with a math content specialist, sharing a class that rotates between two locations. Each could add related subjects like social studies or science, or another specialist could take a third area. Teachers could focus professional development time, standards, and curricula on a single subject.

Students would benefit from teachers who not only understand the content, but know how to teach it well. Teachers would be trained in developmental stages in a given content area, allowing them to deeply reflect on current student understanding and what individuals need in order to advance.

Disadvantages
Completely self-contained classrooms and all the related advantages would disappear. However, if paired well, teachers could work together to establish common expectations and similar classroom climates. Students would still only see two teachers per day. And with today's emphasis on constant change of focus (thinking of video games and t.v....always quickly changing), perhaps it would even help to keep student attention?

What do you think? Are you or your teachers overwhelmed? How can we help teachers to learn all they must know to be successful?