All missing layouts (23 in total) are:
- Circuit de Catalunya - School Circuit
- Daytona - Short Circuit (track added in Update 4)
- Homestead Miami - Mini Circuit
- Homestead Miami - Super-Mini Circuit
- Homestead Miami - Speedway Circuit Alt
- Homestead Miami - Road Circuit Alt
- Indianapolis - Grand Prix Circuit Classic
- Indianapolis - Grand Prix Circuit Alt
- Le Mans - Bugatti Circuit
- Lime Rock - West Chicane
- Maple Valley - Full Circuit Reverse
- Road America - Full Circuit Alt
- Road America - West Route
- Road America - West Route Alt
- Sebring - Club Circuit (track added in Update 9)
- Suzuka - Full Circuit Alt
- Suzuka - West Circuit
- Suzuka - West Circuit Alt
- Virginia International Raceway - Patriot
- Virginia International Raceway - Patriot Alt
- Watkins Glen International Speedway - Full Circuit Alt
- Watkins Glen International Speedway - Short Circuit Alt
- Yas Marina - Corkscrew (track added in Update 2)
I suppose we’re going to see not only new tracks but also returning layouts in updates 
EDIT (November 2024): Since this list is still being referred to, I’ve updated it with 3 missing layouts for tracks added since release. Too bad there are no layouts I could remove from it…