I am a very happy Wyngate parent, so read my response with that mind.
Yes, the school is totally overcrowded right now. I think we have 10 portables in use. An addition has been approved and is going to start this upcoming school year. The addition will be finished and open for use in Fall 2013. You will be hard pressed to find an elementary school in Bethesda that is not crowded (I think Carderock is not), so I definitely wouldn't make that a deal breaker.
I find the Wyngate community to a be a perfect combo of living in Bethesda while not being "snotty" like so many people think of this general area. Families value the great education, are very involved in PTA activities, and the Principal of the school runs a tight ship (in a, I think, good way)...
I know Bethesda well and there are only a couple of other neighborhoods that I might prefer to live in but I couldn't live in a house of this size if I were to live in them...If I were looking to live in the Whitman district, I'd look at Bradley Hills or Wood Acres. But for several reasons I actually would prefer my kids attend WJ, rather than Whitman, so I'm sticking with Wyngate.
Good Luck and if you have specific questions I might answer, ask away!