Grealish has been the standout performer for Dean Smith's side this season, scoring nine goals and creating eight more across all competitions.
The 24-year-old has been heavily linked with a move to Manchester United regardless of whether Villa avoid relegation from the Premier League or not, while the likes of Manchester City and Liverpool have also been mentioned as possible destinations.
Guilbert expects his captain to earn an international call-up in time for Euro 2020 this summer, and also backed Grealish to flourish if he joins a "big club".
"He's a top player. I think he has the ability to go to a big club this summer. The Euro, clearly, it will go," Guilbert told France Football.
Villa are next in action against Leicester City on Monday night as they look to bounce back from Sunday's EFL Cup final defeat to Manchester City.