Actually, no they would not go to Prod. There are allowances in ST that do not fit in Prod. For example - ST allowances for inner fender pannel changes are not legal in Prod. So aged out ST cars might not have anywhere to go.

Put me down as strongly against changing the age limit in ST. I am building an 83 RX7 and all of the fab work is done. It took me two years to get to this point.

One of the reasons I selected ST over Prod is that I felt that the engine swap rules would allow me to keep an old chassis competitive.