What did kennan predict might happen in the soviet union if containment were practiced consistently?

Over time, the Soviet Union would either soften in its stance or would break apart from the internal contradictions of its system.

One of the things George Kennan said in his "long telegram" (8,000 words) sent in 1946 was that the USSR's overall methods of propaganda and control were negative and destructive.  "It should therefore be relatively easy to combat it by any intelligent and really constructive program," he said.  Urging a policy of containment rather than direct confrontation with the Soviet Union was a plan for waiting the nation to change in a positive direction or fail because it could not maintain control of its own system.  Kennan said, "Success of Soviet system, as form of internal power, is not yet finally proven. It has yet to be demonstrated that it can survive supreme test of successive transfer of power from one individual or group to another. ... Internal soundness and permanence of movement need not yet be regarded as assured."