I respect a leave to your imagination ending (even if it is sequel baiting) - and if done well I can accept not getting closure/satisfaction.
But in this case it seemed simply too loose. Wasting time becoming champion assumes that Norton will just let you in. Sports commissioners arbitrarily change rules all the time.
I got the impression Nova deposited Alita's core in Iron City so he could watch her and let her believe she could take him down.... perhaps as revenge for her actions in the past, or just to have something to do.
It could be a deliberate cycle just like the Matrix iterations, as described by the Architect.... and knowing the Matrix inspirations, the Architect was probably inspired by this if it's correct.