I should clarify - what I meant is that if we're shipping GPLv2 software like Busybox, then I'm able to spend billable time improving Busybox and upstreaming my patches. That's labor that could be going to GNU coreutils instead, if it was the userspace on my product. But since I'm not shipping it, that means I don't find bugs or need features very often. Which means I have way less of an opportunity to pitch in.
I'm not making this up either. Even in my personal life I own lots of random devices that I know for a fact are running Linux and Busybox. But I have to go out of my way to find a device that I actually have a chance to get a toolchain running on and can actually start working on patches. It's usually limited to old devices that had no security or had their security broken. So any contributions I make are limited to things that only work on insecure old legacy hardware, stuff that is not going to be of interest to your company working on the next new hotness. There is a real problem here that's in-part solved by the GPLv3, but you have to actually acknowledge that it's a problem.
Ease of contribution is a problem for sure, and it's one that GPLv3 was intended to address. My main point is that the changes from GPLv2 actually had the opposite effect for a whole group of developers.
Instead of encouraging -more- development, I feel like maybe it's just driven developers away and onto GPLv2, MIT, or BSD equivalents. Maybe this is intended behavior, and not an accidental side-effect. I don't know. But it's hard to dispute that it reduces the pool of potential contributors to GPLv3 packages.
GPLv3 components just aren't an option for a lot of products, regardless of whether GPLv3 is better for users (I agree that it is). I think it's really harmed the FSF a lot. With fewer installations of FSF packages, the FSF sees less participation and loses some of its clout. And that makes me sad :(
The developers who relicensed to GPLv3 don't care that some companies won't contribute. From their perspective, any of those contributions would be unusable to them. I feel a similar way with my open source projects -- why would I as an outsider maintain code that nobody outside of your company will ever have any possible way to test in a real production scenario? It's a waste of my time. Yes I might be missing out on minor bug-fixes but I don't really care about that. Like you said, feature development is more important.
As far as firmware-updating goes, to be in compliance the user just needs to have some way to get access to the keys. You don't need to make separate keys, it can be the same method that you use.