Will there be other species in G5 besides ponies? Hippohriffs, griffons, kirin etc.
Or will they retcon that and just have ponies?
The longma of Lauren Faust`s design may appear along with the kirins and dragons in the TV series, there are certainly many non-pony communities in Equestria that may have eventually covered the entire continent when the magic disappeared.
As the ponies have advanced technology that could only be produced through a large market that can cover more than one continent, it means that a very large world will be discovered. As the pegasi - a militaristic people notorious for military conquests in ancient times - control middle Equestria, it meant that they could have trade routes on the navigable rivers, on the major continental roads and the climatic “hubs” under their own control. Queen Haven is possibly the most powerful pony in the whole continent, and of course also perhaps the richest. She has a large empire with professional armies and perhaps airship fleets under her own power, and we do not know about the political conditions, but by controlling Canterlot - she can control the hub of the economic structure of what had been the “Friendship Empire” when Twilight ruled.
It is certain that the Mane 5 will find much new when the magic has returned, if Sunny is determined to rebuild the great empire by establishing new bonds of friendship both inside and outside the older Equestria. We could possibly have candidates for the first “friendship council”, Queen Haven, Argyle Starshine and Alphabittle who will ensure a political union of the various realms in Equestria while Sunny and the rest of the Mane 5 go on adventures and make important self-discoveries such as find new friends, new knowledge - and fight villains. If Sunny will become a permanent alicorn in many years, the “Friendship Council” will have a very important role to play in preparing Equestria for the return of the alicorn kingdom. Haven, Starshine and Alphabittle can be warned about this if Sunny as a temporary alicorn becomes known to them, it is possible that they will witness it themselves.
So Sunny and her friends will be freed from politics when they experience their adventures and spread friendships, in the process of rebuilding the lost after Twilight Sparkle. But they will have powerful forces behind them. The unicorns with magic, the pegasi with their armies and the earth ponies with their strength and numbers.