Making a forward bloc in PMLN isnt easy. Remember we have been hearing a forward block in PML since before elections when Panama scandal started. Even after the senate elections, when Ch Sarwar won, PML new that some of its candidates had voted for PTI however neither did they expelled those nor did those candidates came forward to make a forward bloc.
But yes i agree if PTI manages to create a forward bloc in both PMLN and PPP, than game over for both these parties. Rest assured PTI will sail smoothly the next 5 years.