I don't think the GA market will ever grow that large though - not without substantial effort to make compliance with all the regulations effortless.
You need more pilots, so making it easier to navigate and comply with Parts 61/141/142, with 67/68.
You need more aerodromes; Part 139.
You need more aircraft, that's Parts 21, 23, 33, 35, 45 and maybe 34, 36 and 39 too.
You need more mechanics; Part 66 / 147.
You need more maintenance facilities, Part 21, 39, 43, 145.
There's maybe 50,000 active GA pilots (PPL or LSA) doing it for pleasure regularly? The rest are time building for the airlines, and same for mechanics.
To get that 50k to 500k to 5M actual people ... I think an affordable aircraft is probably the easiest part. Maybe it'll get people interested? Though you can already buy factory-built LSA's for $300k that'll do 150kts (see Risen); Europe already has a booming LSA scene ... but it hasn't really resulted in more people flying, not as far as I can tell.
I don't think an aircraft is the missing link, but I can't express how much I'd love to be proven wrong!