Short answer is NO. The PAC-3, PAC-3 MSE and THAAD serve a different role and it would be difficult to replace those roles with a land based SM6. The PAC3/MSE provide a large magazine (12-16 missiles per launcher) to forward deployed troops including protection from saturated TBM attacks. THAAD provides the ability to go after highly capable (IRBM class) TBM threats from longer distances and allows for these threats to be engaged from the exoatmosphere. Assuming that a large booster equipped weapon is acceptable to the US Army, the SM6 may provide a complementary capability to both those systems but would not replace their unique role in Army IAMD.
My speculation is that if the Army would use the SM-6 it would be at Aegis Ashore sites in the continental U.S. Think it would be the proposed 21 inch diameter variant. It would be used as a point defense missile to protect those sites from hypersonic gliders or as a second shot for the SM-3's of the sites. The latest missile defense review has still left the eastern missile defense site up in the air so to speak. There are 3 finalist locations one of which was to receive GBI's but no decision has been made. Think we will know more after the test of the SM-3 against an ICBM in 2020.