Well there can be another possibility that is not dependent on time travel, but dimension travel.
If we take a theory into account and speculate that there exists 7 dimensions in the FT-Verse.
#1 - Eathland
#2 - Celestial Realm
#3 - Edolas
#4 - Dragon Realm
#5 - Demon Realm
#6 - World Of Great Magic
#7 - Future Realm
The Future Realm could be a realm where time is exactly like Earthland but just ahead by 7 years.
I would also give a explanation of how clairvoyant abilities work. (Magic flows from Future Realm into Earthland as distorted images)
In the Future Realm, someone successfully finds a way, to not timetravel, but rather enter the alternate universe Earthland.
By reverting the events in Earthland it would theoretically alter the events in Future Realm as is in essence exactly like Earthland but 7 years ahead.
This could be possible as, we've never seen a vision the showed events larger than 7 years.
But it also seems to initially contradict itself because of Edolas-based visions.
But in essence, Edolas itself could just be a mirror of Earthland.
"Future-Realms",Parallel-Edolas (and the other dimensions) would then obviously be directly connected to "Future-Realm" and thus indirectly connected to Earthland and Edolas(and the other dimensions)
TL;DR
Time travel and dimension travel is some serious shit.