Gai isn't going to die. But if he dies, it would be pretty lame. I mean, come on man, a technique that was presented back during the Chunin Exams, and was said to be one of the strongest in the Manga, was used in vain. What the hell? Madara's entire left half was blown up, but he laughed at it and even attempted to finish off Guy with the black orb. Then he started healing, like nothing happened. Okay, he's the Juubi Jinchuriki, he's Madara Uchiha, the main antagonist of the story, but come on Kishimoto, don't reveal that technique if you're not going to use it like it's supposed to be used. Guy should've killed the one who gets that kick in the chest, and if he dies, I'll be really disappointed with Kishi's job in the past few chapters.