In our metro-Atlanta school, the Caucasian teachers do not use the expression "on tomorrow." I mention this only because I saw a commenter earlier who said this as well. I don't know if it is ethnic in origin or regional, but as a native Southerner, I never heard it in my entire life until I moved closer to Atlanta. We didn't use it in Mississippi, nor did we use it in North Georgia.

I grew up in North Georgia, and I never heard this expression until I moved to the metro Atlanta area. Moreover, it appears to be an expression of non-standard English used by my peers who are African American. I cannot think of a single Caucasian who uses this expression. I'm in the teaching profession by the way, and I've heard this used daily since I moved to this area 6 years ago. It's definitely a dialect thing, but in my experience it's specific to the southern black culture.