Look at what you call "innovation" today, what is it? Nothing about having locked down computers will prevent random folks from creating another Instagram. Look at the demo day for YC, how many of those demos require that the people install new program code on their "customer's" computer?
But a fully general purpose piece of hardware, could become much more expensive in the future.
I don't know, maybe 20 years ago average young computer hobbyists were writing small OSes, but today, people write websites and mobile apps. 20 years ago everything was simpler. You could learn about ins and outs of 8086 in a week, and it was "practical" to have such low-level access to hardware. Today, the landscape has changed. We should change too.
It is an interesting question, in 1977 the closest analog would be a 'locked down' color TV versus the Heathkit build your own color TV kit.
The other weird thing about this discussion is that none of the hobbiests in 1977 were concerned with the fact that you couldn't root an IBM S/370. They didn't need too, they just built their own computers. That said, anyone could get complete access to an IBM S/370 (one of my summer jobs at IBM gave me full control over one, right down to what microcode we were going to load that day) so the tools to 'create applications' will no doubt continue to exist.
What will change is that there will be a device that people use to communicate and play games and stuff which you can't just buy, install your own ROM image, have it do that other stuff and the stuff you want too. Not that scary.
The Apple ][ cost $1200 at release. In 1977.