Eddie being there is too good (for me) that until February 16th, it'll likely be a "believe it when I see it" case. I will forever wonder how great it would have been if he had surfaced during that great run from 1986-1995 (save for Season 20).
Anyway, I agree that Dennis & Victoria won't have a reason to miss (really no one will have an excuse unless it's an actual legit one). IMO, they'll probably show up but primarily to pay tribute to Jan. Just a guess; they were last there in 1999 to remember Phil, along with Jon, Nora, Mike, & Kevin (Dana couldn't make it due to his recovery from a legitimate "medical situation" IIRC). Though in 1999, it was less than a decade removed from their run, and they had a role in the 25th Anniversary. However, I think they'll be there, but I won't be too surprised if they didn't show up