Dans la letter n°144 (1954), p179 Tolkien explique:
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 metalworkers. 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.
A cet époque il semble donc que Tolkien soit déjà fixé sur ces explications; en 1972, letter 418 p419, Tolkien ajoute:
But I think in Vol. II pp. 80-81 it is plain that there would be for Ents no re-union in 'history' - but Ents and their wives being rational creatures would find some `earthly paradise' until the end of this world: beyond which the wisdom neither of Elves nor Ents could see. Though maybe they shared the hope of Aragorn that they were `not bound for ever to the circles of world and beyond them is more than memory.' ...
Je pense, à la lecture de ces extraits, que les Ents-femmes sont un mystère de plus du Légendaire auquel Tolkien n'a pas répondu, et ce volontairement. C'est ce genre de mystères qui fait la magie de l'oeuvre de Tolkien, en partie tout du moins, pour moi. Un monde trop rationnalisé aurait eu des failles: on en aurait vu les articulations. Grâce à ces énigmes Tolkien passe un coup de gomme dans son oeuvre pour rendre tout cela plus flou. Il s'assure ainsi l'effet de profondeur dont il est question dans la préface du Silm.