Stallone, 67, - who stars alongside Willis, 58, in the first two 'Expendables' films - was delighted the 'Die Hard' star had been replaced by Harrison Ford, 71, for the latest sequel, 'The Expendables 3'.
He tweeted: ''WILLIS OUT ... HARRISON FORD IN !!!! GREAT NEWS !!!!! Been waiting years for this!!!!''
Five minutes later, he added: ''GREEDY AND LAZY ...... A SURE FORMULA FOR CAREER FAILURE.''
While Willis played secretive CIA agent, Church, Ford's part is yet to be confirmed.
Filming for 'The Expendables 3' is set to begin this month with filmmaker Patrick Hughes in the director's chair.
Stallone co-wrote the script with Richard Wenk who was also his screenwriting partner on last year's film.
The first two instalments in the franchise have earned almost $575m worldwide.
The action film is expected to be released in August 2014.