Okami may not have sold all that well when it debuted on the PS2, but it was most definitely well received amongst critics and fans alike. Apparently, rumours and whispers spewing forth from OPM says that there may yet still be life in the series for this generation of consoles.
The rumour section of OPM claims that there might possibly a sequel in store for the PS3, and probably other platforms as well. The unique gameplay, charming ensemble of characters and moving plot was all that was needed to capture the hearts of those that played the original, and taking into consideration the new motion technology, a sequel isn't entirely unfeasible.
Still, it's just a rumour, and considering the stigma left between Capcom and the now dissolved Clover Studios (now Platinum Games), it'll be interesting to see if Capcom does go forward with a sequel. After all, Okamiden just released on the DS.