It is most likely actually scalloped rather than cupped, and this is normal wear for any higher mileage motorcycle tire front or rear. Ride on it until the wear bars show; or more properly until just before the wear bars show; and then replace it...
By all means, continue riding on your worn-out tire. When it blows you can tell us how lucky you were, assuming you survive.
I look at it this way: there are two tires, only two tires, that keep me from becoming a smear on the road. I don't want to become a smear on the road, so I make sure that my tires are good. If I have doubts, I replace them. I hate to spend the money on them, especially when they are 'not quite' marginal, but I'd rather pay $300 to replace old tires than spend a fortune on wheelchairs over the rest of my life.
A forum community dedicated to Suzuki Burgman motorcycle owners and enthusiasts. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more! Open to all 200, 400, and 650 models!