I doubt any exclusivity deals are in place, pCARS 2 still has the road going GT86 and a range of Toyotas have been added to Assoluto Racing recently.
PCARS 2 has a bit more than just the road going GT86:
2013 GT-86 (road G)
2013 86 (road G) (= LHD version of the GT86)
2015 GT-86 Rocket Bunny Street (= tuned version of GT86, road C)
2015 GT-86 Rocket Bunny GT4 (= fictional GT4 spec version that runs in the GT4 class)
1998 GT-One (GT1 class)
1999 GT-One (LMP900 class)
TS040 Hybrid 2014 (LMP1 class)
There are 2 possible reasons that make sense to me:
1) From the rumors over at Forza it was said that Toyota didn't like their cars to be "modified" in games (not sure if that means upgrading or painting). In PCARS2 you cannot upgrade cars (only tune them) and at least on consoles you cannot paint them either. So that could be a reason they still have the license. Maybe Toyota's request for Forza and NFS was that cars would not be able to be modified anymore in those games and Microsoft didn't agree on that and hence there was no agreement. That could be the reason why Toyota answers "ask Microsoft" as to why almost no Toyota cars are in FM7 anymore. Similar requests do happen you know, if you look at the Ferrari's in Real Racing 3 there are limited to painting options compared to other cars. That Audi Sport quattro in Dirt 4 is the only car that can only be raced with the standard racing livery and not the monotome colors like all other cars. Chevrolet demanded at Turn 10 to remove the "SS" logos from all the cars and that the name was changed for example to Chevrolet Nova Super Sport instead of Chevrolet Nova SS.
2) Another reason could be that Assetto Corsa and Project CARS 2 simply signed the license deal with Toyota earlier, before they started acting difficult. Assetto Corsa already exists from 2014 on PC if I'm not mistaken and PCARS 2 got announced spring 2015. Since Toyota was still in FH3 (release september 2016) and the 1992 Toyota Supra 2.0 GT Twin Turbo still made it in as a DLC car in December 2016. So Toyota's new license restrictions are fairly new. Dan Greenwald (Turn 10) once said it takes about 6 months to make a car from scratch to completed so that 1992 Supra must have been fairly new and designed somewhere early/mid 2016. If Toyota changed their mind around that time, it makes sense PCARS2 and Assetto Corsa already had their deals signed.
One thing I find really weird is that the GT-One and TS040 aren't in FM7 anymore either, same for the WTCC Avensis. The only car to return from FM6 to FM7 is the NASCAR Camry but that's most likely since it's licensed via NASCAR and not via Toyota. So some race cars have been cut as well, not just road cars.
Since Lexus is not in FM7 anymore either I expect the same will happen with NFS PB.
Whatever the reason behind it I'm curious to see how it all evolves in the future when new games are released in 2018 and later. I sure hope it can be sorted out with Toyota in the future, a game like FM7 just doesn't feel complete with a big iconic manufacturer missing and in NFS 2015 Toyota was a big brand as well.