My biggest concern is whether it will be "brought back", as in another event, or here to stay permanently. Suppose it's an overwhelming success -- can we look forward to always being able to play it, or is it going to be brought back for a few weeks at a time twice a year? Because Arena is exactly what I've been looking for ever since Dominion became kill, but it's going to be really hard to get invested into it long-term if I have to play on Riot's schedule and not my own.
If it's an overwhelming success, then a permanent version is definitely something we're going to be working on.