From what I have heard, the EN-EL3e is compatible backwards with the EN-EL3 and 3a, but not the other way around. The 3e has 3 contacts whereas the earlier ones only have 2. I presume this has to do with the battery status monitor of the D200. A call to Nikon might yield some info, but I would wait until the D200 is out, I'm not sure Nikon tech support has been brought up to date.
I wrote to Support at NikonUSA to ask this question. I told them that I realized that the EN-EL3e has addded capabilities. What I wanted to know was if in a pinch I could use an EN-EL3 in the D200 to provide power only and not have any of the additional capabilities. They informed me that this would work.
you will see a whole bunch of pictures of the camera and accessories. In particular, there are two clear shots of the EN-EL3 and EN-EL3e. You can see that the slots are different. The newer battery has the bigger slot, so it is backwards compatible. But the old battery will not fit in the D200.