Aggro is going to be the only strategy after rotation unless Theros has some serious shit to make up for what's missing in the core set. Farseek leaving is a big deal for midrange and control decks, so is Think Twice/Thoughtscour. That's how control decks hit their land drops consistently and get to their big spells. Add to that the manabarbs for nonbasics and we'll be seeing a lot of linear mono or almost-mono colored decks next season. UWR doesn't use Farseek but it loses Pillar for dealing with Voice, and again, not having access to Think Twice or Thoughtscour is a big deal.
Green actually loses all of it's mana fixing in m14. Elf that only produces green, and no rampant growth, farseek, wild growth, etc.