Can someone (a judge) clarify this? Are you saying that Flamespeaker has to still be on the battlefield for you to play the exiled cards?The biggest danger with Flamespeaker is if your opponent is smart and/or lucky, he can hold off until after you reveal the first card or two and use his removal before the damage step ends and keep you from casting any sorcery speed effects that it revealed.
The way I read it you can play the cards until end of turn, regardless of whether he survives combat.