Besides the fact that Print is accessible, like everywhere else, through Ctrl-P, the "gear" menu can be opened with the keyboard by hitting Tab until the focus goes to the toolbar, then using the arrow-keys to move focus to the gear icon, then hitting Return.
Oh yes, tab arrow key return. How obvious. I mean, sure it's obvious to you and I, but even KDE has menus which are obvious to anyone who's used a computer before. I don't think most people who haven't will even know what a gear is, or why it would make sense for it to be used for settings. Woops, that's not even what they're using it for, is it? Fail, fail.
GNOME should stop trying to invent the new thing in the mainline. They're not very good at it. That's okay, most people/projects aren't, but most people/projects accept that.