It is difficult to say for sure, he DID commit suicide, but it is highly likely that he would have. Many other Germans generals, von Kleist comes to mind, faced trial in the Soviet Union and elsewhere after the war for crimes both real and imagined. It seems that the Soviets WERE intent on putting him on trial for the actions of 9th Army/Army Group Center in the retreat from the Rzhev Salient in March, 1943; wells were poisoned, settlements and foodstuffs destroyed, and many civilians were either shot or simply rounded up and deported to the Reich, to serve as slave labour. I'm sure there were also other war crimes that took place under his command, likely to do with the commissar order, and with the destruction of settlements and shootings in connection with 'anti-partisan sweeps'. Throw in other Nuremburg Charges such as waging aggressive war and crimes against peace, and it would seem that suicide was the best choice for Walter 'Front Swine' Model.

This is pure speculation, but the Americans might also have pursued charges against him, or at least supported his trial, in light of the actions of Army Group B during the Ardennes Offensive. Hitler had commented before the offensive began that the soldiers were to advance at all costs, and I believe this included comments about not being slowed down by prisoners. In light of the Malmedy Massacre and the Wereth 11, they might have held Model to the 'Yamashita Standard' for these actions, as commander of Army Group B; again, this is pure speculation, as the man had no intention of surrendering as a Field Marshall (especially given his contempt of Friedrich Paulus), and committed suicide in the Ruhr Pocket.

TL;DR: Yes, he likely would have faced war crimes charges, but the chances of him being 'taken to Nuremburg alive' would have been slim.