Yeah James Maddison deserve to join a big club at least playing in Premier League, no matter which club it is. Leicester City is a mediocre club, they were struggle against Championship club e.g. Blackburn Lovers. I don't think Leicester City will able to get promoted in the next season if their performance are like this.
Madison is a transfer target of Manchester United in some seasons and some big clubs put their attention on Madison too. Leicester City decided to keep him in the club but with only one star player like Madison, he can not pull the whole Leicester City squad and this season shows that in football, you need to have a good squad with at least 11 good players. If a club has only one star player, they will not get good result and Leicester City is a good example.
Years ago when they won Premier League, their squad did not have star players but they had good players and good coach that worked hard together. Some of their players became star players in Premier League after that successful season like Riyad Mahrez, Kante, Vardy, Kasper Smeichel.
Vardy's prime already passed, he's currently 36 years old and his market value is only 4 Million Euros, he should be happy if Leicester City still want to extend his contract.
Vardy is too old and he is no longer good enough for Leicester City and any club in Premier League. He shined too late in his career and Leicester City is where he touched a golden time of his career. One Premier League title is enough for Vardy and he can satisfy with this big achievement. His name will be in the hall of fame in Leicester City forever.
I believe if Leicester City keeps Vardy, he will want to play and retire in Leicester and will not move to any club.