Much has been said about the uncertain fate of the Entwives. It is often stated that Tolkien himself didn't know, or didn't write anything certain about them.
However, I'm reading "The Letters of J.R.R. Tolkien" and came across this passage in the letter 144:
"I think that in fact the Entwives had disappeared for good, being destroyed with their gardens in the War of the Last Alliance (Second Age 3429-3441) when Sauron pursued a scorched earth policy and burned their land against the advance of the Allies down the Anduin (vol. II p. 79 refers to it). They survived only in the 'agriculture' transmitted to Men (and Hobbits). Some, of course, may have fled east, or even have become enslaved: tyrants even in such tales must have an economic and agricultural background to their soldiers and metal-workers. If any survived so, they would indeed be far estranged from the Ents, and any rapprochement would be difficult – unless experience of industrialized and militarized agriculture had made them a little more anarchic. I hope so. I don't know."
What are your thoughts on this? I think I agree that Sauron would exterminate most of them, and enslave others (if such beings can ever be enslaves).
There is extensive discussion on the Ent Wives in the character section. Load to read. I love the thought of The Entwives.