I don't think so for Chimera, they already are in the game as Seth Killan said, why would they have them running around in the background of the map; he also said they may be hidden somewhere else.
Also, I would really, really hope for Crash, then I could buy the game.
If the DLC is Third Party orientated then it'll cost money.
I´d love to see a DLC with a Chimera and Abe as rivals. The Chimera are actually quite similar to the Sligs in Oddworld...they are half alien, half machine. The Sligs were ordered to suppress Abe and his friends and kept them as slaves. The Chimera could try this as well and Abe would again be trying to save his friends and escape. So a Chimera and Abe would work out as rivals.
The chance that this will happen is like 1%, but an Abe fan may dream.
This would be an amazing rivalry and Abe is my most wanted character and Chimera is in my top 6. I would kill for Superbot to do this.
Characters I expect we'll see?
Big Boss/Solid Snake
I know that everyone really wants Crash and Spyro but I doubt it will happen. Wander/Ico are not going to be in. I also wanted to see Ethan Mars and Chell but I think Quantic Dream will be in the same boat as Team Ico and I doubt SuperBot will try to aquire Chell.