According to hiro mashima himself on volume 49 we still have a long way to go. Now however long that is who knows but were certainly heading towards the climax now that the manga is starting to explorer major plot points of the story.
With this new empire he can make something good, without dragging. Now he still got this:
-current arc with Alvarez and everything that's going on;
-E.N.D stuff, more backstory of how Mavis died, since we know from FT Zero some stuff, but Zeref mentions in chapter 436 that he'll save his relationship with Mavis for later, we can find out what Lumen Histoire can do, if God Serena is indeed Yuriy Dreyar;
-he could make (hopefully he will), a longer flashback of what happen in the Dragon Civil War, how Acnologia became the Dragon King, Zeref could've been involved in a way or another, around that time Igneel tried to stop E.N.D but couldn't;
-the stuff with Zeref & Natsu learning he's his brother, how he meet Igneel...
-Lucy's mom might appear, since many fans theorize that her death has something to do to how the dragons disappear, we can learn that;
-battle between Natsu & Acnologia, battle between E.N.D & Zeref, fight between E.N.D & Gray, Gray finding out that he has to 'slay' his best friend.
There are still things that need to get answered & that can happen without Mashima rushing the story,