I think in terms of large publishers you might see a decline but where EA, Activation, and other publishers stop others will rise to take their place. Not to mention there are already great single player titles availible from multiple studios in the work.

Not sure if this counts as an "Action Adventure game" but the .Hack G.U series was released on Steam last month as ".Hack//G.U. Last Recode" it's a .Hack game so its got a Anime style theme but basically the plot is Glitchy sentient game locks people inside, puts people in comas, and you have to solve the mystery. Played them when they were on the PS2 and really enjoyed them myself. Game attempts to simulate a "MMO" environment in a single player game and while it doesn't really work I still enjoyed my time with them. Might be worth a look if you have slugged through all the normal recommendations.

I am slightly biased in that I have only played Black Flag mainly because I was always told they were very hit or miss. I actually did not play Black flag until well after Syndicate came out which again heard it was more of a miss than a hit.

Witcher 3 to me is always going to be a great comparison to any new RPG that comes onto the market. Witcher 3 strikes a great balance between Story and game play. Witcher 3 has systems in place to craft items, but has mechanics in place so you don't have to constantly re-craft everything over, and then bitter about using bombs or potions. Story is relativly quick if you blitz through but the world has a lot to offer along with it being relatively deep + reputability is high. I'd say my opinion haven't changed right now but I am always looking out for a better game. If something would come out and would be as good or better I woulden't be mad, I would be happy that Witcher 3 and Cd Project red raised the bar.