Ikumi Nakamura (background designer for Okami) and Hideki Kamiya (director and story lead) took to Twitter to express their want of a new entry in the Okami franchise. It's not quite a confirmation, but the desire from both of them seemingly confirms they're working on making it happen. The Tweet urges fans to message Capcom to express their want of a sequel.
"Okami is going to be back! We want to make Okami sequel and fans are looking forward to it too. You guys want to see Kamiya’s Okami again, right, everyone?"
If the Tweet is to be believed at face value, "Okami is going to be back" is a really strong indicator of a sequel happening with Capcom's approval.