I would like to see some more enemies make a return or even brand new ones.

Almost certainly.

(But probably only in the 'new areas' added by said DLC)

I hope new enemies are added. Not that I don't get a challenge out of current enemies, just walking into a new location its so easy to predict what kind of enemy I will be facing.

there is a 99.9% that we geting new enemies, new power armor, new stuff for settlements and new weapons

I made a mod for Skyrim that integrated some of the DLC enemies into parts of the main game world where appropriate. Hopefully I can do the same for Fallout 4, and get that mod on the consoles. Lol, that's like the one mod I ever did that was noteworthy.

Personally, I want to see Centaurs again. I miss them. They're way cooler than these Mutant Hounds.

Add to that, new companions. To be clear, I'm very satisfied with the current lineup of companions. I'm just not satisfied with the current lineup of romanceable companions.

For sure there will be more enemies. I believe Broken Steel (FO3) added some heavier Enclave troopers at posts around the Capital Wasteland itself. They were not only contained within the DLC "space". I know Dawnguard and Dragonborn added new enemies within the land of Skyrim as well. Each was done very well and each expansion had it's own DLC space as well as enemy spill-over to Skyrim propper.

Super excited for DLC.