I expect a fight in 3 phases:
- First phase Shanks will take the fight lightly, underestimate Kid, gets some surprising hits, Kid seems being stronger.
- Second phase, Shanks realizing his mistake, going into full fight, is clearly superior to Kid, but Kid isnt going down totally.
- Third phase, Kid pushes himself to a major upgrade, most likely something around CoC or Haki overall, so he seems to comes close to shanks.
At the end, Shanks will be still superior, but would need to go high high diff to beat Kid, but the fight will be interrupted by the giants, or by Saul, so they leave it. Shanks than claims he underestimated Kid extremely and can see him alongside Luffy being part of the new generation and he steps back, aknowledging that Kid would win next time if he keeps growing like this.