Well, all other things being equal (which is to say that once I actually SEE it and have an idea of whether I will like it at all much less enough to indeed buy it that I WILL buy it), I will buy 5E because I enjoy the idea of being able to put forth a new campaign and run a game where players are not experts on how things work, where I can bend, break, omit, and modify rules to suit myself and my players wherever I want to without anyone - ESPECIALLY players - telling me I'm doing it wrong.
I will enjoy creating new classes, implementing both new and old mechanics, finding new and better ways to play, REDISCOVERING older yet superior ways to play. I will revel in creating an entirely new game world from scratch, or in the possibilities in adapting an old setting to new ways to do things, and celebrate with a huge $&*#-eating grin on my face the FUN I am going to HEAP upon my players whether they're ready for it or not!
I am going to love the freedom 5E will give me to jettison ALL the baggage of the past, laugh at the grumblings of Luddites and Grognards who wouldn't know a good time anymore if they sold it in a game store with a "New and Improved!" sticker on the front, and leap blindly and gleefully into a better future for D&D.
Again, all things being equal. Here's hoping...