There may be a market for a "microkernel" redesign of browsers in the next 5 years. OP's point is right that the current design is impossible for new entrants t

There may be a market for a "microkernel" redesign of browsers in the next 5 years. OP's point is right that the current design is impossible for new entrants to implement. That alone probably won't create a market for something new (in no small part because the 2 major engines are FOSS) but if we hit an intersection of new technologies along with a need to rapidly adapt the Web to new computing platforms (eg AR/VR) then it could certainly happen.