I don’t expect the game to be around forever. No idea if I’ll leave it or it’ll leave me. I’ve been playing about three years and haven’t seen any signs that it is in decay but I’m no expert.
I looked at the article in your screenshot and it is from 2012. I think that points to the nature of game cycles more than anything else.
I would be surprised if Zynga has plans to shut it down anytime soon as they haven’t even finished paying for the acquisition of SGG.
Edited to add link to a post with much more info and insight!