it sure is looking like the compact line is going to be discontinued at some point. to me though one of the best part about the compact line is the fact that there are no bodies in the chain or other points of failure. I have a hard time believing though that the line was not successful enough to have them continue to be made.
To be nitpicky, the compact line had electronics in the XLR housing. So really, you could think of them like other active cable solutions, its just that the active cable did not plug into a typical mic body, but rather a mic "body" in the form of an XLR connector housing.
At any rate, I don't think their "success" had anything to do with it. I think this is the relevant quote from the gearslutz message Scott posted:
the big thing being that this new line allows for balanced connections from mic to preamp whereas the old compact line was unbalanced between mic and XLR. This should especially help with shielding for RF interference.
My guess is that DPA sees the 406x micro line as the mics that will be used to be nearly unseen for theater/live performance applications. The compact 402x line was for unobtrusive applications, where it was not desirable to have the mic have a large visual footprint (but not to the point of "unseen" like for performers wearing them at a theater performance like the 406x).
I think the quote above is the issue -- the 402x line was unbalanced between the mic capsule and the XLR, and therefore more prone to interference. With the growing amount of interference sources (including cell phones), DPA which strives for perfection, did not want to have a product that is subject to as much interference (and resulting poor performance) as the unbalanced compact 402x line.
I'm sure they think that for most applications, either a miniature mic like the 406x will suffice, or for less unseen applications, the new "short body" solution provides as much unobtrusiveness as is necessary. Obviously our little niche prefers the compact line, but I'd bet they simply were not happy enough with the performance in re: interference that the compact line provided.
