Still seems odd to me that they wouldn't at least announce that "Yes we were able to find Marco Polo, but we still need more time to properly restore it. Stay tuned." Fans are going to be excited and buy this thing regardless, and in fact you'd probably build the anticipation up even higher by doing that.
Yeah yeah, I know. The BBC likes to do things their own way.
According to the rumors I've heard, the reason for this is that when the BBC announced the recovery of Galaxy 4 well in advance of its release on The Aztecs DVD, they didn't sell as many as had been hoped. As a result, The Enemy of the World and The Web of Fear were only announced at the same time they became available on iTunes, so as not to let the excitement die down. The time to expect another announcement is when Marco Polo is ready for release, and there is no other big Doctor Who news on the horizon to interfere with it.
At least, that's what I've heard. I'm not saying I necessarily believe it.