Those are great news my friends, firstly:
"We're open to the idea of custom PvP matches, which would allow for duels in the arenas. There are a lot of decisions before we can get there, but on the design philosophy front we don't have anything against practice duels or other custom matches (1v4?)"
and secondly
"but I've seen some people start to get ideas that it's going to be an eSport, and that's just not something we're targeting"
I think that it says all