I am almost a 100% sure they will be saved somehow. Either another marine drops by and intervenes (smoker?), Gap will get up or ajoki will save them with the argument that they are worth more alive than dead. Keep in mind that garps status and fame is quite important to the marines and by some extent to the world government as it would be a big blow to their reputation if garp would be killed, so I think they could use them as bargaining chips and Blackbeard always has a bigger goal as he is quite cunning.