I don't think so (I would say that, right?!) because of the time in which they were used. By the summer of 1863, the Confederacy's hope was really pretty much over. The Union had control of the Mississippi and had the entire Southern coast blockaded. The only place where US and CS were on relatively even ground was along the Potomac, and after Gettysburg, another CS invasion attempt was unlikely.
In late 1864, when Sherman was burning my fair city, the CS was already out of it in this part of the country. Confederate forces had been running from Sherman since Tennessee--they knew they couldn't stand and fight. It may have sped the end of the war by a few weeks, but even that I doubt; the end of the war was marked by Lee's surrender to Grant (there were still Confederate forces fighting after April 9, although few and far between), which was going poorly for Lee. Sherman and Sheridan's campaigns didn't really change that.
What the March to the Sea did accomplish was plenty of ill will. Lincoln might have had a pretty sounding inaugural address about "malice towards none," and all that, but it was a load. CSA wanted to be an independent nation, and it lost that battle, but after such tactics as Sherman and Sheridan used, Southerners would have found rule by the Northern part of the country more oppressive than before. The thoroughness of destruction in the South followed by an ineffective occupation most likely was a key contributing factor to the rise of the KKK and assorted vigilante groups, and the South became a horrible place to live--for both blacks and whites--for a century to come. I'm not saying Sherman was responsible for all of that, but he played something of a factor.