yoda-sama said:

Did the canonical status of the original Clone Wars series officially get stripped? If so, did it go out the window with the Expanded Universe, or sometime before that (in short, explain this canon purge)? Also, does the CG Clone Wars series ever deal with the events directly leading up to Episode III?

Disney did not de-canonize the Expanded Universe. Because it NEVER was officialy canon.

From the first Zahn trilogy they said (Lucasfilm) that if Lucas ever wanted to make movies set after ROTJ the stories could be totaly different.

Disney just sent a reminder to people who forgot that fact. (of course they could have decided to adapt the books, but in this case it would have been a "canonization" of the EU)

(And yes, the first CW series is not canon since they started the CG one. Don't know if it ever was canon by the way. Just know that the CG on is canon. So the other is obviously not.)