If this is done from a marketing view point, it's a big mistake - no-one's going to buy the sash shirt with a sponsor on it when they can get the plain one a few weeks before.
But if they're doing it just because it looks fantastic and they want it to be "the" shirt of the new Saints era, then fair play. The only reason i'm not happy with keeping the sash is because we can't seem to get away from the come on you reds chant.