First, belts in tires do not shift or slip. That is an old wife's tale. What is really going on is irregular wear - which is caused by mis-alignment and aggravated by insufficient rotation practices and insufficient inflation pressure.
So rotating the tires to see if the wobble changes is a good diagnostic. If the wobble changes, then the alignment is causing irregular wear. The question is: After the alignment, will the new position of the irregularly worn tires develop a new wear pattern - erasing the old pattern? Good question - and it depends on how bad the tires are.