The numbers don't lie, anyone who kept track of the numbers, also knows that the number of raidguilds in the past few years has been dropping considerably faster than the number of subscribers. 25m guilds were the first ones to bite the dust, but even HM and normal 10m raiding is seeing guilds die at a rapid pace ever since MoP.
The reason can be summarized very simply:
"Lack of new blood."
There are many reasons why new people are having such a hard time getting into the raiding scene, but to name the two most important ones:
1. "Applications". It's perhaps not the applications themselves that are at fault here, but examplary of mostly the high standards that many raidguilds have, they tend to only want to recruit people who have exactly the same gear as them or are ahead of them in progress and experience. People who are new to WoW usually won't gear up with anything than LFR and Valor gear and will have a very hard time getting accepted into any kind of raidguild. If guilds don't learn to lower their standards and to have a friendlier policy to letting new blood in then in the longterm they'll run out of anyone to recruit at all. This is a typical example of internet entropy, there are no governing bodies or studygroups that can investigate and prevent crises on the longterm. If WoW raiding had been a 'government' concern, then there would've been all sorts of recruitments measures that would force guilds to recruit newbies to assure longterm prosperity of the raiding scene, just like how modern governments need to take all sorts of measures to protect the economy or the wellbeing of subgroups, just to present a poignant comparison.
2. LFR. It satisfies the needs of most people nowadays. The average gamer tends to be very happy beating a game on easy-difficulty if they get to see same parts of the story. Few people will actually see the point in doing it on a harder difficulty setting, especially if this will mean time commitment. People simply don't like commiting to online clans and guilds as much anymore as they used to. The market has been spoiling them with the comfort of playing casual and quick games that they could pick up and drop whenever they feel like it. The NES generation is no longer the main part of the market. On the other hand though, LFR was clearly introduced because the raiding scene was dieing off... and if the raiding scene had become even smaller than it was at one point during Cata then the plug would have been pulled on designing raidcontent at all. LFR is the guardian angel of making sure people will have raids in the future, it wasn't a great or longterm solution though ... because it aided at the same time with the decline of normal or HM raiding.
There is very little doubt in my mind that in the future raiding in WoW will entirely consist out of queuing or flexi-raiding at easier difficulties.