A 2 level demo for RE5 looks like it's set to hit January 26, 2009 for the xbox (Heard 2/5/2009 for the PS3).
I enjoyed RE4 even if it was a departure from previously Resident Evil games. The "Ganados" were not really traditional zombies per se, but parasitically control creatures that moved much quicker than previous iterations of RE baddies and utilized weapons and from what I've seen of RE5, the creatures will be similar.
RE4 had more of an action feel that earlier incarnations in the series and it definitely pulled away from the ammo conservation game, but the play and feel were a solid fit. I expect that Resident Evil 5 will be similar to the its prior game in terms of feel and play but will still sit solid in the series.
The addition of co-op play is just the gooey icing on the brain cake.