I seriously doubt SE is going to change up the content cycle. I'd be pleased if they did - I quit around Patch 2.4 out of boredom, and only recently returned to catch up through the Heavensward storyline - but I'm not expecting it. I fully expect to quit again shortly after the release of 4.1 if it appears to be mimicking the same structure followed by 2.x and 3.x.

I also second the notion that the limited scope of the cycle is also a huge problem. Having such a rigid pattern is bad enough; when the rigid pattern involves relatively tiny amounts of content (oooh, two new dungeons; oooh, one new 24-person Raid), it makes things much worse.