Makarov could not have gone out in grander fashion. Protecting his children from the most powerful dragon of them all. Talk about an amazing guild master.
What really got to me was Laxus urging everyone to retreat and Natsu berating him for it until he saw those tears. This has to be hurting Laxus most of all, Makarov raised him since he was a child.
I'm going to agree with Fenix here, Gildartz should be appointed Guild Master, he's the most suitable. That being said I wouldn't mind Laxus, but he's still kind of young. His reformed mentality however, is very befitting of the position. Down the road I'm sure he'll be appointed master, maybe the epilogue.
The central plot of the dragon's history and the Dragon King's Celebration should start to unravel itself now. What happened the day all the dragons disappeared and Lucy's mother "Died", July 7th, 777? Zeref's likelihood of being a slayer continues to increase. That still leaves 3 more to go though. Hopefully Mashima introduces them all gradually and doesn't just save them all for that specific arc. Well at least show two, and perhaps save one for the actual event.
For clarification Acnologia is indeed the dragon which Gildartz encountered while on his 100 year quest, and which instantly defeated him and dismembered his arm and leg. Acnologia was the reason Gildartz failed the quest. Whether Gildartz' mission directly applied to seeking out Acnologia or if their paths only happened to cross was never explicitly stated. However, Makarov's musings after Gildartz reported his failure seemed to imply that his mission did have something to do with the dragons.
Natsu seeing a dragon would of course get his hopes up, since it confirms that they haven't died out and that Igneel also has a good chance of still being alive. (Which, unbeknownst to Natsu he is)
There's still Tartaros and Raven Tail to think about to, can't wait to see where Mashima decides to take the plot next. The S-Class Promotion Trial/Grimoire Heart/Zeref Reawakening arc was one long roller coaster of twists and turns and I loved every second of it.