I saw it mentioned on another website's forum that was talking about the changes for 2016 Wranglers. I honestly can't remember which website I saw it on. The other changes I remember them mentioning are two new special edition jeeps and that Tank is only getting a partial run on early 2016s before being discontinued too.
Anvil has been a very popular colour. I've seen a ton of '14s and '15s in that colour and kinda wished they kept it to the 10A / X / HR special edition line, but if they're discontinuing it then it will become a lot more unique. Apparently they're coming out with another non-metallic grey colour that will replace it, but I don't know how that shade will compare.