For me, the cost-benefit ratio is a very important factor in e-reader upgrades. I like an e-reader because it's an example of a single-use tool that does one thing and does it well. I like the absence of backlighting and the absence of distractions caused by multifunctionality. When I just want to read, nothing beats an e-reader. But that doesn't mean I want to spend as much on a single-purpose tool as I would on a phone. That's a major reason why I didn't buy a Forma - for less than $150 more, I can replace my aging phone with a powerfully-spec'd 6.4 inch Android 8.1 device. So any improvements to e-reader screens, for me at least, would need to come without a massive blowout in price. I could not justify spending more than around $200US as an absolute maximum for an e-reader, and if that means sticking with ~300dpi, I'm fine with that.