I loved 4 and 5, so I'm definitely down for 6. I would have liked to see Claire back though. It's been a while.
I would like to see Co-op handled like RE2 handled the multiple storylines. 2 characters that are off doing there own thing but interact every now and then although it wouldn't be necessary. They would be able to communicate the whole !@#$%^&* though. So one character would be experiencing things and telling the other "I just saw some crazy monster, if you ever come across this area watch !@#$%^&*". Sometimes the scariest thing can be someone describing a possible threat. And if there are parts where they might worry about the other breaking tension the communicator can malfunction. I think that would be a cool concept.
!!! That would be soo awesome. Exactly what I would like. Playing with a body and only meeting them once in a while while talking over a radio (heaset) that is not working all the time. Then you still got the feeling of being alone but also have the chance to mix in some awesome player player interaction every once in a while. If you need some matches for a candle for instance and you can't seem to find one and tell your partner about it and he is like "Yeah, just saw some in this huge kitchen back under the stairwell"... and you go there and find them.
It can be though to implement though since you can't really make a scenario where both have to be there at the same time. What if one takes it very slow and the other one just rushes through? So it has to be playable totally on your own while still being able to interact when in the same place at the same time.
Awesome example you hear you body call out to you on your radio that he is just fighting this totally huge monster in a yard and you then try to go up to the roof and shoot it from the top. But you don't have to. The other player can defeat it on its own if you don't make it it time. It is hard of course.
Problem would be a player death as it would look strange if you from the roof see the other player die and then immediately reborn somewhere...
just some thoughts... because the idea is awesome!