I'd be very surprised to see a new track, though I'd be down if we did get one. As for cars, I'd say it's anyone's guess, which I kind of like. I can only assume that most cars we get for a while will be from the datamined list, though the operative word is "most," as some of the VGTs and the Corvette C8 were not in the list IIRC.
I don't think we've gotten a new Bonus Menu in some time, either, nor any new missions, so I think we're due for those. I'm still a little surprised we haven't seen a Lamborghini-themed Extra Menu yet, nor one for McLaren, Dodge in general, or Aston Martin.
My bet is that if/when we get such Extra Menus, the following cars will be required:
Aston Martin - DB5/V8 Vantage S/DB11
Dodge - Challenger/Charger SRT Hellcat/Challenger SRT Demon
Lamborghini - Miura Prototype/Gallardo/Huracan
McLaren - 12C/650S/F1 (I know the F1 is expensive, but the F1 is McLaren, so I don't think you could have an Extra Menu that omits it.)
Other ideas for Extra Menus are as follows:
Group B - Lancia Delta S4/Audi Quattro S1 '86/Renault 5 Maxi Turbo
Group C - Jaguar XJR-9/Mercedes-Benz Sauber C9/Nissan R92CP
Gr.3 - Nissan GT-R GT3 '18/Subaru BRZ GT300/Porsche 911 RSR
Jaguar - E-Type/XJ220/F-Type
V12 Lamborghini Models - Countach LP400/Murcielago/Aventador
Classic GT500 - Toyota Supra (A80) GT500 '97/Nissan Skyline GT-R (R34) GT500 '99/Honda NSX GT500 '00
And if I had to just make stuff up using cars from my personal wishlist, here were my picks:
LMDh - Cadillac LMDh-V/Porsche 963/Acura ARX-06
LMH - Toyota GR010/Ferrari 499P/Peugeot 9X8
Italian SUVs - Ferrari Purosangue/Lamborghini Urus/Alfa Romeo Stelvio Quadrifoglio
American Pickups - Ford F150 SVT Raptor/Dodge Ram Rebel/Chevrolet Silverado ZR2