The USMC & USN leaders involved in the Tarawa campaign, and amhibious ops in general choose to look at the Betia battle as a near defeat tactically. This suggests what they would have done had the attack been repulsed entirely.

1. Preperation. Air and surface reconissance had several failings. Future operations had more thurough reconissance.

2. Preperatory Fires: Armor piercing ammunition was not used. The high explosive projectiles from the ships used fuzes with instant action or very short delay. The same for the aircraft bombs. Realitively few Japanese bunkers were damamged because of this. Subsequently the preparatory fires included a large portion of armor piercing or penetrating type ammo.

3. Communications failed. This was found to be a radio problem. The radio operators became casualties, the radios were immersed in water, the radios were destroyed by enemy fires, electromagnetic interferance with the signals interrupted messages... Subsequently there was more cross training for radio use. If the specialist operator became a casualty, there were others capable of using the equipment; Water prooffing improved; leaders and operators learned to be more flexible in getting he message through. If the signal would not go through on the Naval Gunfire Spotting Frequency then the message would be relayed via the battalion tactical frequency, or the administrative channel. Messages for fire support had absolute priority and had to be sent via any radio and any channel that would work.

4. Distribution of explosive charges and flamethrowers was inadaquate. The assuallt engineer teams became better integrated into the rifle companys. By 1945 USMC rifle companys were in effect assualt engineer companys. Similarly the number of MG available to the company comander was doubled, then tripled.

5. The M3 Light tank was useless for the assualt. The M4 Medium tank became the sole assualt tank and the light tanks regulated to auxillary roles.

So, I'd guess a complete repulse would result in more of the same, a evaluation of what was done wrong and improvements implemented. Keep in mind the Betio attack was not the first or the largest amphibious landing, or assualt, to date. There had already been a half dozen such operations in the Pacific theatre and one defeat would not be a show stopper. In Europe the failure of the Dieppe raid did not bring a halt to amphibious operations. So its unlikely the overall strategy in the Pacific would change. Or even the operational technique. Just the tactics would be modified, much as they were continually improved anyway.