I would certainly prefer that this be the case, but I also don't think it's particularly likely to pass as legislation - because there are plenty of devices that are sold at a loss, expecting to make it up on other later software sales.

I believe almost all modern game consoles live in this space, I would expect Amazon's Kindle devices are in this category, etc. And while I don't like this model and won't participate in such ecosystems, neither can I deny that such things are fairly common and popular. Forcing open firmware on those would likely generate a much larger, and, frankly, better funded response to being able to maintain a locked down firmware for the useful life of the system.

Picking specifically on the "no longer receiving firmware updates" category makes it much harder for those companies to argue that having to do this will hurt their profits or hinder their ability to recover losses on subsidized hardware - they literally don't care enough to bother updating them at this point, so it would be much harder for them to make these claims. You abandon a device once you're done earning your money back on it. I doubt Sony, for instance, still expects much return on deployed Playstation 3s. And it's exceedingly hard for Apple to argue that they're making any money on an iPhone 3GS or something, because it doesn't even run modern app store packages.

So my logic here is that "you must unlock abandoned devices for those who care" is likely to be winnable, whereas "All devices must be unlockable from day 1" isn't.