The futile quest for the light and lethal Future Combat Systems was one response to that problem. The Stryker brigades are another. But even these light armored vehicles are better suited (when up-armored) to counter-insurgency and would probably be smashed by enemy heavy armor unless we had absolute air supremacy capable of smashing enemy armor in contact with a Stryker unit. Besides, the Stryker never did solve the strategic mobility problem because we don't have sufficient airlift to deliver multiple brigades in a time frame faster than shipping them by sea.
The traditional response has been prepositioned unit sets deployed afloat or abroad that are maintained by a small unit and which can receive troops quickly flown in to marry up with equipment. We are practicing this in South Korea right now:
Demonstrating the ability to rapidly equip forces for any crisis or conflict, the U.S. Army is off-loading and upgrading pre-positioned stocks from USNS Watson (T-AKR 310) at this commercial seaport on South Korea's scenic southern coast.
Together with several military units and commercial organizations, the 403rd Army Field Support Brigade (AFSB) is conducting the operation at the port until mid-December when all of the equipment will be loaded back on the ship and taken back to sea.
This would be key to reinforcing our single brigade in South Korea to a full division's worth. Ship in a Marine regiment from Okinawa (soon Guam) and two heavy brigades using prepositioned equipment, and we have a potent strike force to back the ROK army. We have practical experience from 2003, when 3rd Infantry Division troops (a heavy mechanized force) fell in on three brigade sets of equipment sent to or in Kuwait.
We have a couple Army brigade sets near South Korea, a couple in the Persian Gulf, a couple afloat, and one in Europe. The Marines also have such floating unit sets (one, at least).
See this AUSA piece on the Army's program. It seems to me that this program, expanded to meet our deployment needs, is far better use of our money than trying to build a light, air transportable tank replacement that the Air Force will never have enough transports to lift in sufficient numbers in a short enough period of time.