It’s very hard to find definite stats on this, but the ratio tires:brakes seems to be somewhere between 2:1 to 3:1. So the overwhelming majority still remains. The other problem that remains is that microparticles that have settled will be pulled in the air again by passing cars.
Hopefully we'll see some more research on this as time goes on. I strongly suspect that there is a tradeoff between traction and microparticle production. Very grippy racing tires tend not to last long.
If you could have some sort of traction assist device like a rubber block on a piston that hit the ground for emergency braking, you could get away with lower traction on the wheels normally, and modern electronic controls could make the whole thing stable and relatively transparent to the driver.
First we'll have to overcome the slow motion catastrophe that is gasoline direct injection.