Well, yes and no.
1.0 allows for 19.39Mb. Most stations are providing 3-4 (we have one here doing 8!) "sub channels" Each channel has it's own dedicated bandwidth. Most stations started ATSC 1.0 with just one, maybe two channels. As encoding got better, they were able to add more and more channels to their stream.
3.0 allows for 57Mb! So yes, they will be able to put more "subchannels" on OR allow more bandwidth for each channel (if you're watching OTA 1.0 for things like the Superbowl or AGT, or something that has a lot of motion/confetti, you'll see macroblocking... that's because that individual channel is "bit starved"... not enough of a pipe to fit all of the data).
Eliminating 1.0 will NOT give a station more bandwidth. It will just "turn off".
1.0 & 3.0 signals each take up ~6Mhz of broadcast space.