I don't consider the current raid encounters to be very suitable for pickup groups. With just 10 players in a raid, the organizational difficulty the LFR feature overcomes wasn't that big anyway. And the actions of any single player count for more, making the raid more vulnerable to disconnected, afk, or just plain bad players. And while Blizzard plans to make LFR raids easier than the current version, I'm not convinced they can actually do much: The difficulty of current raid encounters is 90% having learned the dance, and just 10% playing your class well. When Gevlon recently got disappointed by the new WoW raiding he remarked that it was easier now to make a raid with undergeared players and voice chat than with overgeared players without voice communications. Game by Night Chris feels the same, saying "Players who don’t talk simply cannot complete raid content in today’s WoW." But LFR pickup raids will have to do without voice chat, because there are too many different systems, it is hard to organize for an instant pickup group, and many current non-raiders don't even have the relevant software installed.
That leaves us with two possibilities: Either LFR will fail, because pickup groups won't even be able to do raid content on the new, lower, difficulty level designed for them. Or Blizzard will have to nerf raid encounters by staggering amounts or remove features. If you have raid encounters where a single player standing in the wrong place can wipe the whole raid, that raid encounter would have to be nerfed to the point of being not recognizable any more to allow a pickup group without voice chat to complete it. By having made raiding all about learning specific encounter scripts, Blizzard has closed the door to successful LFR pickup raids, and I'm not sure how they are going to pry that door open again.
[EDIT: Seems the LFR raids will be 25-player only. Ignore what I said about 10-mans.]