Babysitter takes over or some miracle allows Round 2. Imu will probably focus on Nidhogg and Ragnir now until Luffy's heart hits that beat.
Or Imu could go after Gunko considering the earlier comment regarding Brook and Shuri...
Either way, plot will allow Luffy to recover and come back once more but it will certainly be interesting to see how Oda plans to ignore this wound. If his heart is destroyed, maybe Lilith can make him a new one with the organ tech from Egghead.