Dark_Messiah said:
now that F.lucy and P.lucy meets the future already alter.
Not necessarily. Time traveling can be factored into the "regular" timeline. For instance, in OVA #3, we see that the "Memory Days" book exists because the MC's went back in time with it, creating a action loop that fits the present reality (Makarov finds the book, MC's use it 6 years later, book goes back in time, Makarov finds the book). Each MC's interaction with their past selves didn't materially change the present, either.
Given that Charles' prophecies also occur in the present, it seems that you can't change the material facts in the future.
At the end of the day though, it will depend on whether if Mashima will stick with the "deterministic future" or if he'll go with parallel dimensions.
I don't get why did Princess put trust into shady looking character like Future Rogue.
F. Rogue told the Princess what would happen in the tournament, so he used what he knew about the future to dupe the Princess into believing everything he said.