Encoding for BD is a bump down as well. You cant make a mountain out of a mole hill. Your resolution is already set to SD. Throwing higher bitrates at it wont make it better….just SD with with more bitrate.
Maybe you’re confusing quality and resolution? Of course all this depends on using high quality encoding. All bets are off if you dont have a good encode for DVD to start with. In other words, the eye wouldn’t be able to see the difference between a properly encoded MPEG2 stream for DVD and the same stream encoded for H.264 for BD at 4x the bitrate.