depends on what you see as the being "the plan", I see it that he had a 5 year plan to replace all the over-paid players that feel they are owed a place in the team whilst putting minimum effort in, with young, hungry players that want to play for the club and reducing the wage bill at the same time. These players will need to time to adapt and learn the ways of the premiership and some players will not be good enough so will move on but did not cost the earth anyway so were not a high financial risk.
He is not even half way through that plan yet and has already made a significant impact whilst keeping the clubs premiership status (which was always going to be at risk given that he took on a team of relegation candidates and then began a mass player replacement).
Alex ferguson won nothing with United during his first 5 years at the club despite inheriting a better team than PL did here. We may not know the full depth of PL's plan, his targets or indeed his daily attempts to improve us but we do know that our wage bill has reduced, our players are making an effort and Lambert has not finished his plan and has not run out of ideas.
If we replaced our manager every two years we will never get anywhere because the re-building will just keep starting again and again. He needs time and our backing. When he is done we can criticise, complain or enjoy his success. Time will tell but you cant write off his work when you havent seen the finished product.
In Lambert I trust!