You have ask, is anybody else improving their tanks? I'm out of the loop these days, but are the Sov, er, Russkis or the PRC developing a new generation of tanks equal to or exceeding the capabilities of the M1A2? I don't see it.
I think the real revolution will along the lines of lighter vehicles.
Both the Russians and the Chi-Coms are improving their tank designs. I don't think anything on the table actually leapfrogs the M1A2 in terms of capabilities, but they are certainly closing the gap. If we want to stay ahead, we will have to replace platforms more than once every 5 decades.