1.) An interesting person to die would be Yamato, even though I like him. I say "interesting" for the following reason. If Naruto is unable to control the 9 tails, then Yamato is the only one who can suppress it when Naruto goes 4 tails and above. Given that the 4th's seal is weakening, it is more likely to happen if Naruto doesn't learn self-control. The only other two ways are Sharingan, which Sasuke has. The second is the seal Jiraiya left to Kakashi. Thus, no one themselves could shutdown Naruto. If Yamato dies, then expect Naruto to learn to control the 9 tails himself during sage training or the seal being tightened. I'm not saying he is the front runner, but it could be a major issue if he does die.
2.) Also, those interested in Naruto getting a new uniform, myself included, recall that Naruto needed to get a new headband because Jiraiya trained Naruto so hard (Naruto says this when he returns). Given that the toad's sage training is more difficult, one can speculate that he will need some new gear.
3.) If Konan uses her origami technique, Kakashi would spot it in a heartbeat if his Sharingan is active because the paper would emit chakra. It would have to catch his suspicion first though of course. If someone uses a water technique, she's kind of screwed. Recall Pein had to stop the rain jutsu for her to use her disperse/recon jutsu. Further, Jiraiya easily stopped her with oil and his hair.
4.) Pein (given only what we know of his ability thusfar) is going to have his hands full if he invades Konoha, leaving Tsunade out of it, the other elite shinobi are diverse and powerful enough for the six bodies (Kakashi, Gai, Yamato, Neji,...). I hope some of this is on point. Thanks
Kakashi being hospitalized is a very good point. However, Jiraiya and Tsunade agree the Kakashi is a given for Hokage and that Naruto is a long ways off before Jiraiya leaves to find out about Pein.