I think that's one thing that would actually make sense. Maybe they're more open to the idea now that they're publicly supporting and advertising third party displays. (edit:spelling)
They've always supported third party displays, but this is the first time that I recall that they've included third party displays in an Apple event / presentation. To me, it's a pretty sure sign that an external 5K display from Apple isn't immediately forthcoming (else they would have announced it now and not mentioned the LG display).