In an interview on ew.com, Cuse and lindelof said that "the narratives are always in chronological order. We are not going to mix narrative order." This would then exclude flashbacks and flashforwards in the same episode.
I am willing to bet that the diehards will respond to you that you can have a flashback, THEN a flashforward and they would still be in chronological order.
I read the same interview and came to the same conclusion as you. They are not going to deliberately confuse us so that we have NO idea what's going on, they just want to surprise us now and then. Seems simple enough to me.
