I would suggest brushless will be used for many years to come not just 2.
IMO Lipo is not the future of RC cars as lithium based batteries are extremely dangerous when things go wrong. Once they light up on fire you cannot put them out until all the lithium has been burnt up.
Buildings have been burnt down due to lithium batteries, I have been using lipo for 4 years in my helis and planes to only have one battery go up in flames. This destroyed the plane, radio gear, motor and started a grass fire.
I have had Lipos swell up and be on the edge of explosion several times before I shut the charger off and did what ever I could to cool them down.
I have always taken the upmost care with Lipos and ulitmate performance was not the goal in my flight activities. I can just imagine what would happen in rc cars where ulitimate performance is the goal. I would expect to have a Lipo go up in flames at least every month and possibly costing thousands in damaged equipment due to a $150 battery.
I no longer use Lipo and I went back to Nimh in the RC air activities as well.
I have had a couple of Nimh cell die and I have only ever had one explode. There was a bang, horrible smell and some black mess. IMO this was nothing compared with problems caused by Lipo when things go wrong.
IMO what should happen is all classes bar novice/540 stick pack racing should go to 5 cell. But the weight of the car must remain the same.
This will reduce the need to use expensive light weight materials, reduce the expense of hop ups ie no need for titanium screw kits, carbon parts ect. This will also allow manufactures to beef up the drive train and make the cars stronger and result in less maintaince and less replacement parts. You will save money on hop ups, save money on batteries, and not need to buy new equipment, the end result will be that the hobby will be slightly cheaper.
Novice/540 could probably stay using a 6 cell stick pack.