Discovery Island is Physically still there, but closed when Animal Kingdom opened. All the birds were moved to Animal Kingdom. Rumor has it that the bird droppings are extremely toxic, and as a result, has to be cleaned up before the island opens again for whatever use Disney deems appropriate.
River Country has been closed since the drought 3 years ago. The bacteria level in the lake increased, and Bay lake is now closed for swimming. Since River Country gets its water from Bay Lake, it too is closed.
FW fans have been holding out hope that Disney can come up with the money to renovate River Country so that it no longer uses water from Bay Lake, and re-open it as FW's "themed pool"