To be clear this decision should be made between the '26 and '27 season. I just don't see him costing 30m/yr in 2028.
And yeah, it's assuming he can be the #2. That doesn't mean he has to produce close to 1k yards next season-- in fact that seems impossible with Lamb, Pickens, and Ferg on the roster.
If they believe he can be a complimentary #2 to CeeDee, then you go to him next offseason, offer around a 3/42 extension which ends up being around 11m/yr until 2030.
If you wait until Pickens is off the roster and Flournoy puts up 800yds 7tds, then yeah... he's going to be more expensive.