Squre Enix has a followup to its original iPhone RPG Chaos Rings in development for iPhone release this May. Famitsu (via Sokuho) reports this week that the game will be set prior to the original, presumably making the word "prequel" apply.
A true sequel is also on the way. Square Enix bought out space in the magazine for a teaser ad for a "Chaos Rings II." Since this is just an ad, we'll presumably have to wait for official announcement before we get some details.