I'll go on a limb and claim for publicity and political fallout reasons there will never be enough BVR RoE airspace to make BVR relevant to aircraft design.
There's a difference between the classic definition of BVR meaning slinging a missile at a blip no one has seen 30 miles away, vs the F-35 concept which is to have excellent sensor suite leading to the pilot having excellent situational awareness so the pilot can shoot down the other plane before the other plane knows they're present, etc.
Its tricky to get into visual range to visually identify the target as a mig-21 and not a 767 full of civilians without at least some dogfighting performance.
There's a difference between the classic definition of BVR meaning slinging a missile at a blip no one has seen 30 miles away, vs the F-35 concept which is to have excellent sensor suite leading to the pilot having excellent situational awareness so the pilot can shoot down the other plane before the other plane knows they're present, etc.
Its tricky to get into visual range to visually identify the target as a mig-21 and not a 767 full of civilians without at least some dogfighting performance.