I'm just a bit disappointed since I used to think Kojima made each Metal Gear quite distinctive from one another, look at how different MGS1 (Alaska, underground bunkers, industrial settings, modern), MGS2 (Big Shell, oil rig, massive boat to explore, Arsenal Gear, slightly futuristic) and MGS3 (Jungle, enemy bases, 70s era) all are from one another.
I think, for the most part, that still applies. Peace Walker was just a re-tread of MGS3 territory with new mechanics to play around with, sure, but I think MGS4 certainly had its own identity. Maybe not in such obvious terms as being able to say "tanker/base/jungle", but it definitely felt very different from its predecessors, in the same way each of them felt different as they came out.
I think it's a little early to be saying that this one won't be distinctive, considering that we haven't actually seen footage from it yet. The one pic of Big Boss isn't much to go on. The information that he kills guys, rides a jeep, and crawls around could have basically been applied to any of the previous games as well.