It's believed that original plans had Asuka pinning Jax to retain, but they ended up with a double count out finish after brawling on the outside of the ring. There's no word yet on why the finish was changed.
As noted, tonight's RAW will feature a rematch with Asuka defending her title against Jax.
There's been speculation on a similar finish happening on tonight's RAW, which would then lead to a stipulation match at the WWE Extreme Rules pay-per-view on July 19. That has not been confirmed, but we should have a better idea of what the direction for Asuka is after tonight's RAW. WWE has seemingly been building to Asuka defend her title against Charlotte Flair soon, possibly at SummerSlam.
Stay tuned for updates on plans for Asuka.