The way it's announced, it looks like a new series of sorts, Fariy Tail Zero.
I hope it's canon, because this is the perfect place to stop otherwise if there is no good amount of manga material to work with.

The Doranbolt part was funny as hell

Since this seems to be the start of a timeskip, let's go and speculate!
How will they power up?
For the dragon/demon slayers, do you think they'll figure out some sort of transformation (like dragon force), or just be far more powerful with the same attacks.?

How can Lucy become stronger? She relies on the power of the spirits, who were mostly just lacking in power this arc. It's hard to imagine she'll train in the spirit world, since time goes by só much faster there she wouldn't get anything done. Even if she figures out how to summon 3 or more spirits at the same time, how will that help? Bypassing the requirement for summoning the Spirit King would seem like a cop-out of some sorts.

I really hope the 'lesser' members of FT get something noteworthy too. I'd love to see both Elf and Lisanna be more useful in the future. Lisanna especially has been nothing more than fanservice up till now. Give her some good new powers.