870 barrels are relatively affordable. I would seek a shorter barrel for the gun if you were looking for a more agile gun in the woods. I agree with others, the performance would be marginal at best if you were to cut down the 26" barrel. I own a 21" barrel 870 and a 26" barrel Benelli. I really don't notice much of a difference in handling other than the 870 is easy to carry through brush and thick forest with its shorter profile.
A 26" barrel is pretty universal for most purposes. It's not too short that you couldn't take it out and shoot doves or clays with it and it would still purpose well as a turkey gun. If your gun patterns well now, I would leave it be! Just my 2 cents for what it's worth.