It's affecting the price even now. We already dropped to $257 from a stable week of $267.
The real drop will probably happen like per op, when/if the chains actually split, for now they're identical.
Imagine the drama when/if someone sends coin from core to service on xt after the split, and it never confirms..
No doubt it will be fixed, but for a certain period, it will be interesting.. imho sell now, and rebuy @ 220-230 under 3 months from now, easy 15% profit.