I hope so. They can be anybody except Omid&Christa. For me, they are new characters or they are someone we already know from season one (like Lilly but not Molly,if I'm not wrong there are some players out there who left Molly bitten on episode4).
But I'm pretty sure they are not Omid&Christa. They are gone. If they were them, we should see this scene at the ferry not on a lonely field, right? Is Telltale trying to surprise us?
I don't think so.
Lilly is a different character than the comic Lilly and as a Lilly fan if Telltale decides to make her the second protagonist, I'm totally ok with the idea! (I see Kenny lovers' faces :P)
And I think the main reason for seperating both Lilly's was because of their need of using game Lilly in the future somehow.
Anyway, she is a killer now and this "killer" theme seemed familiar to me. Lilly murdered in front of a little girl. It may create a good drama with a reminder:Clem around

.
All are my predictions, though.