Sorry to break it to you, but don't count on it. The Ents advance on Isenguard after the orc legions march off to Helm's Deep. The few remaining scatter at the sight of the Ents. The Ents and Hourns scare the crap out of the orcs and the only weapons they have against them are axes and fire. Fire being the deadliest and most painful death for an Ent (one goes up in flames in the book, not sure if we will see it in the movie). Axes are pretty bad too, but it would take many, many axe blows to kill an Ent, and you can guarantee that anyone who hits an Ent with an axe once will never get a chance to swing a second time.