Incredibly unlikely. First, it would have to fail in a way that’s possible to fix. We don’t have robots that can replace screws, solder joints, and polish mirrors in space. Then we’d have to design a brand new spacecraft and mission. That would take years, lots of money, and political will. NASA would likely cut its losses, document the lessons learned, and try again.
I was watching a documentary about James Webb and they claimed that NASA has plans of using unmanned robots to potentially refuel it but no mention of fixing.