If Xander signs an extension and struggles or gets hurt, it's a net positive for him.
If Xander signs an extension but plays like an MVP this season, it's a net negative for him.
If Xander doesn't sign an extension and struggles or gets hurt, he just doesn't opt out and it is no change to his current position.
If Xander doesn't sign an extension and plays like an MVP this season, he'll get a monster deal in FA and it's a net positive for him.
The only risky avenue is him signing an extension and providing play that exceeds his contract.