Will okami have a sequel?

[Grey Acumen]

It's not poor sales that make it impossible for a sequel, it's the fact that the people with rights to the IP aren't the same as the people who developed it.

In order for a proper sequel to be made, Platinum Games(I think that's what Clover studios reformed as) would either have to buy the rights from Capcom, or essentially be hired by capcom as an external team to work on the sequel.
Either possibility is highly unlikely and would be incredibly rare occurence within the industry as a whole. I think I've heard of one other case in which a reformed studio bought rights from the parent company for a game they worked on whiel in that parent company, but i can't remember what it is.

Now its different if all you're asking is; "will there will be any game called Okami 2?"
In my opinion actually stands a good chance. While it may not be have any of the quality that Okami brought out when it was done by clover, it's likely to be tapped on if only for the unique character pool.
If there isn't a full Wii version made, then I'd say there's a good shot at being a DS version made.