It seems to me our heroes just traveled seven years into the future.
Considering this is a shounen story where main characters are rarely older than twenty, I kinda doubt we would see Natsu or Erza seven years older.
I'd situation with characters will be similar to Tsuna and others in Future arc in Katekyo Hitman Reborn! manga.
They will most likely return to the present, possibly with Ultear's abilities, if she, hopefully, appears again in story.