I will be surprised if they do another game. Or at least it will be open world (which could be interesting)
I really enjoyed Blacklist. I thought the story was somewhat interesting and I didn't have a problem with Ironside being gone. The thing is that it was a mutual decision to have somebody new. He couldn't do the motion capture part of the performance so he stayed on as a narrator and adviser. Considering Ubisoft changed the character of Sam Fisher when it was first released based on Ironside being the voice actor it, I don't think they did out of carelessness.
I also enjoyed the co-op campaign and co-op survival mode. They were ****ing fun. The only thing that ruined the experience was the last mission/boss. It was a quick time event and it was ****ing unforgiving.