ABUJA - Nigeria's currency is forecast to edge up against the dollar in the next week to Thursday, while Ghana's and Zambia's may weaken, and Kenya's should remain steady, traders said. NIGERIANigeria's naira could gain slightly in the coming week, supported by central bank dollar sales and subdued foreign-currency demand. The currency was changing hands at 1,485 naira to the dollar in street trading. ZAMBIAZambia's kwacha is likely to be on the defensive because of sustained corporate demand for hard currency. "We see it remaining stable, ... dollar demand is equally supported by supply," a trader said.