Ryan,
Actually Isaiah begins his Messianic writing in chapter 52:13-15. He introduces Jesus' physical condition at the cross (52:14) and His kingly reign (52:15).
I see the tense changes as revealing the redemptive motif of the chapter. It is interesting that all the references to the Messiah are past tense until verses 10-12.
The atoning work of the Messiah is complete (52:12, "Yet He Himself bore the sin of many, and interceded for the transgressors."), His second coming and kingly reign are yet to come.
