Typically, games like these are known to have a shelf life of 3-5 years. K&D has been around for about 1 year on IOS and a bit less on Android. Its based on a model that is not sustainable where the gamemakers have to continuously release new content that creates stats inflation in order to continue the nickle and diming cash flow from their user base. At some point the "balance" in the game gets so out of whack and the game loses its integrity. The revenue drops to a point where it doesnt make sense to support the game, starting the downward spiral that leads to the game's shut down.

So what makes it any different from other internet based games like say, Everquest, Vanguard, DoAC, Star Wars, Rift, etc. Most of those types of games run well for a couple of years or so, then players start to get bored, subscriptions close, less updates put out, and so on. Sure, some go on to do ok in Pay to Play (aka Free to Play, but pay to do anything but the most basic - hmmm, that sounds familiar) and sometimes you win the jackpot ala WoW. They continue on, but at a fraction of their starting population.