[Erundil]

Though it is logical that there would be Huorns left in the Old Forest, since Fangorn and the Old Forest were both outliers of the great forest that once stretched across most of Eriador and Enedwaith, they need not have been Ents who became tree-ish. They could be trees that were becoming Ent-ish, which is what it seems that Old Man Willow was.
I think that there may have been a possibility that the tree that Hal saw in the Northfarthing was an Entwife, I can't be sure and Tolkien never explicitly says what it was that was seen (at least not to my knowledge), so I can't make a judgement one way or the other.