I've heard these rumors as well and to be honest I'm a little split on the matter.
A) I absolutely love REmake2 and was sad that the experience was over after I'd beaten everything (except for the Soul Survivors bits because I didn't find them interesting), so in a way I would like to see more gameplay.
However:
B) I don't necessarily want to see a Marvin DLC because they could just reinvent Outbreak for that, as that's where you see Marvin prior to RE 2. That and I feel that I know what I need to know about him. Ya know. He dies.
So,
C) Yes I want DLC in kind of, There Must Be More kind of way, but at the same time I don't know what they could do to really expand on the story beyond what we really know.
And kind of off topic, I'm more excited about Project Resistance and the single player game it's attached to if I'm being totally honest. I thought it was fun and I also find it intriguing that there is a whole other game that we don't know about because all we got was the multiplayer angle.