I thought someone said that Warlock was the former name for the Hexblade, which was later changed...
However, let's hope this Complete Adventurer has really something new and good, because I cannot think of how it can be filled up to 200 pages...
I didn't like the Complete Warrior, but it had a good point in trying to be useful to every class, based on the fact that more or less everyone makes some attack roll early or late

. The came Complete Divine: much better "crunchy bits" IMHO, but alas it is not much a book for every class anymore, and it goes back to the 3.0 classbook line in concept. Same will be with Complete Arcane. I really don't expect much from Complete Adventurer, so I am hoping for some surprises...
The old Song & Silence was the worst book in the 3.0 classbook series, probably because there was not much to add to Bards and Rogues and what was added was not well designed (it had the worst PrCl ever

).
The few useful bits from S&S have already been revised and pulished in PHB (feats, traps) and Complete Warrior (feats, equipment), as well as its best PrCl. What's left in S&S is flavor stuff - which obviously won't need a revision - and the remaining PrCl, most of which were terrible.
So, what else is going to be in Complete Adventurer?
Wilderness stuff? I though that was what the environmental series was all about...
Skills? I believe they are covered enough.
Sneaky combat? They should have thought more about it in Complete Warrior, if the feats there weren't enough.
Bardic stuff? Why leaving it out of Complete Arcane?
Equipment? After Arms & Equipment Guide, it's hard to find something new and interesting.
With all these in mind, it seems to me that Complete Adventurer will be the least interesting of the series, with just a bunch of boring crunchy bits and revised material. At this point it could be even worse that Song & Silence.

I hope I'm being pessimist and that CV will completely surprise me for good, but I almost wish they were not doing this book at all rather that making it badly...