The raid will be split into 4 wings in LFR, i suspect that you will have access to 1 or 2 the the first week then the rest gets unlocked the week after once people have defeated the end boss in normal.
I'm going to guess that the first 3 bosses will be released the week after release. Then the next 3 bosses will be released the following weeks. So I'm guessing you won't see Lei Shen until 4-5 weeks after the patch is released.
Section 4 will probably come out right before the release of 5.3 lol, crybabies ruined the purpose of LFR.
By the time Section 4 comes out hardly anyone even needs the gear from it anymore, as we'll have much better from valor, normal and even heroic modes.
I don't know how this makes sense though, they drop the same ilevel of loot right?
Yes, all of them drop 502 gear. In my opinion releasing it over the course of 4 weeks (5 if you count the first) is rather slow, so I'm hoping they won't do that. I'm expecting them to either release all of it at once, but keep the "you have to clear the first wing to unlock the second wing" or, highly unlikely, release 2 wings at the time. The first week of 5.2 should have LFR closed, the same way they did HoF(?) and ToES.
Makes sense for LFR content to be delayed, I just hope they won't gate the normal/hm instance like they did with T14. Over a month until all were accesible, whilst normal TOES was actually easier than normal HOF.