That is the basic conflict here. I think for a couple of the players, it would become a rather constant reminder that he wasn't in his chair at the table. If they group were not already pulling close to dealing with the BBEGs, it wouldn't jump readily to mind - but as it is I have the thought that pulling it more quickly to a close might be better than adding more BBEGs for the future. Every good story has a beginning, a middle, and an end, and it may be that we want to end this one, and start a new one.
Well, go with your gut. You don't score points for self flagellation.
If nothing else, maybe put it on hiatus, and come back to it in a year or so you guys can vanquish some evil in your friend's memory.
Talk to you crew. You knew that already. And the good thing about hiatus, is it has no expiry. Maybe y'all will pick it up again, maybe not.