It was scrapped, because there's no official arcade plugin for XenForo 2. Additionally, the arcade we had before the upgrade wasn't very stable as it was an abandoned beta... A lot of the games I installed weren't working properly. It was very tedious to maintain.
I figured we'd concentrate on what we do best: Forum discussions. There are plenty of websites specialized in online flash games that have much better games than what we can find in any forum arcades.
Antimatter Dimensions was added because I thought some of us would like it. It requires zero maintenance and took 2 minutes to add.