A few things, in no particular order:
-Rebels win
-Syrian civil war continues, between secularists, domestic Islamists, ISIS, Druze, Alawites and Kurds.
-Oil prices skyrocket
-Labour, Respect, Greens, Plaid and SNP grow in popularity in UK.
-US House votes to not approve war or fund war. War Powers Act showdown occurs. Possible impeachment of Obama/Biden. (If vote occurs after Hersh's article, say hello to President Leahy.)
Long term:
-Syria unstable.
-Mideast also unstable.
-Israel facing more terror attacks.
-Labour distances themselves from Blair.
-Democrats and Republicans supporting war primaried out.
-Seymour Hersh wins prize for his LRB reporting on Syria.
-Iran buys S-300s.