IMO, Lucas and Lucasfilm has done a simple phenominal job of tying togetether the EU Material related to EPIII. It all meshes and flows in ways I can only begin to imagine, from the Clone Wars television Series, to the Novels, to the comics, to the Republic Commando video game.
I have a theory on this.
When the novelizations began to come out in the 80's and 90's, an effort was made to keep them true to each other, but not necessarialy to the movies. This led to a large mixture of stuff being published, much of which didn't all quite mesh together.
Now we're onto the early trilogy, which for so long has been off limits because people didn't know anything about it, and Geroge Lucas is taking extra special care to make sure everything flows - it wouldn't surprise me if we saw the EU Material related to the Prequels get an official recogniztion as Canon, because it doesn't conflict with any of the movies, only with some of the other EU Material, none of which fits together as well as the new stuff and the new movies.
And no, you won't be seeing the Z-95 in EPIII. Apparently Subpro (Developer of the Z-95) and Incom (Developer of the X-Wing) were screwed out of their place in the Star Wars Universe and years of accepted discussion on the generation of the X-Wing and TIE Fighter have been pushed out the window by things like the "Tri-Fighter" and the "ARC-170". I'm not saying it's a cool looking ship, but there's certain things that I've come to accept about the Star Wars Universe, EU material or not, and I'm greatly disturbed by the mass changes that are affecting that core beliefe.
Official Lucasfilm line is that the ARC-170 is supposed to be in service around this time, and is a front runner to the X-Wing design, however, the company that produces it is neither Subpro nor Incom, yet is going to go on to design the X-Wing.
Regarding the Dreadnaught...given their usefulness in the game Rebellion and their general statistics from other bits and pieces of data, I was under the impression that they (and the Z-95) were much older then a mere twenty years. However, two things are possible. They may have existed before this war. This is unlikely because supposedly there we Clones on board. I say supposedly. They may come into exsistance anytime in the next twenty years.
As I stated I had a long discussion with other SW Freaks about the Teaser Trailer when it was released and there is some speculation that the CIS Ships are front runners to the Dreadnaught Design, just like the Republic Assault ships are front runners to the ISD Design.