The non-convergence of design
This will seem obvious to many people, but I've met people to whom it's still not obvious.
There is a lot of discussion about convergence. Originally, it meant between TV and the internet. That's still happening, in a variety of forms. It's also being applied to mobile - as in, responsive design means you can merge your desktop and your mobile websites into one, without sacrificing the experience of either.
But there isn't, and won't be, a convergence of print and web design. This would be news to some people.
Years ago, tool makers like Adobe tried to make it happen. There were so many talented print designers -- all very comfortable with designing on a computer -- that surely we can give them tools that will allow them to painlessly apply their print design experience and skill into online design, right? Except it didn't work out that way.
Designing for the web requires an understanding of how content is entered, stored, edited, approved, transmitted, displayed, searched, ranked, scraped, fed, repurposed, cached, and archived. None of those concepts are present in print design applications like Photoshop or Illustrator.
The days of thinking that web design tools would "mature" until they looked and felt and worked like print design tools is over. I'll admit that most tools used in modern web design still aren't very mature, but the direction they're maturing in is completely different.
It's complicated, but it's exciting, because a website has a much richer relationship with its viewer than a print publication does. If you're a print designer waiting for tools that obscure all those messy internet details and just let you design on a simple canvas the way you're used to, you're doing it wrong.