No it won't be a rivalry. Unless you figure teams don't have to play each other to be rivals.
At present--and until U of Nebraska comes up big in the wills of Warren Buffett & Paul Allen, it will remain a simple fact of life that Nebbie has less prospect of joining the Big Ten than Moo U or any other Big 12 school not named K-State, Baylor or TX Tech.
Some day, maybe, when Nebbie has the Buffett-Allen billion dollars or more in upgrading its programs and facilities, and it has grown up to be a real university and not a mere after-thought to football, things COULD be different...but that also would require respect for higher education that Nebraskans, like their U of Miesery clones, have yet to demonstrate.
They play Division 1, BCS football---and have a sub-Division 3 legislature and state government.