There's not going to be a Caldari-Amarr war. There's no lowsec space between them, there's only 1 system that's even a border, and that's only because of a "highway" gate (Niarja-Kaaputenen).
CCP aren't going to create a whole new region, with all the complaints that it would generate (moon minerals, effect on 0.0 logistics), just to satisfy the wishes of a tiny minority of RP'ers who like the ideas of Caldari-Minmatar alliance or Caldari-Amarr war, or whatever.
There's barely even a border between Amarr and Gallente too, so the most that is likely to happen in my opinion, is reduced payments for "allied" complexes.