I think that the "tank era" is about over. They plainly have become obsolete. To the helicopter. One AH-64 Apache can take out a handful of tanks, and they can just sit there with their teeth in their mouth. Until the tanks can defend against an air attack I think they are obsolete, maybe even extinct someday.
Maybe tanks would be superior against a country with no helo's, but they are obsolete when the helicopters show up. I do know that some situations are very important for tanks, but thats only a few. Just watch the number of tanks to helicopters is going to get more lop sided as the years go by.