If by "dead," one means "declining in popularity," then yes.
The Cover 2 or Tampa 2 was one of the defenses that everyone thought about emulating due to the success of Tampa, the Bears, etc. But they're realizing they don't have the guys to run it and are dropping it.
Same w/ the 3-4, look at how many teams switched to that after seeing the Pats win w/ a lot of 3-4 packages (not to mention the Steelers' continually dominant D's). Unfortunately, it really sucks if you have too many D lineman and just decide to convert 2 or 3 of them into linebackers...
Obviously the Tampa 2's still great, if it wasn't, then the Bears wouldn't be the No. 1 D in the land.