Here's an idea: Game Maker, Construct 2, Stencyl, MMF2, Unity, and Game Develop can all coexist happily. Neither of them need to worry that the others' existence threatens their own. This is for a few reasons:
1. Many indie developers use/own more than one engine (I own licenses for MMF2, GM, Stencyl, and C2 myself)
2. Competition between game engines gives rise to niches (e.g. C2 is THE HTML5 game engine. Nothing else compares. Meanwhile, Stencyl is for flash developers and app developers who need native exports, and GameMaker is for control-freaks who need power and don't mind learning a new scripting language, Unity is for 3D indie developers that need powerful tools)
3. When an engine DOES fail or fall into obscurity, like I'd argue GameSalad might be doing right now, other game engines learn from their mistakes and adapt, leaving slightly fewer good choices on the market, but making all the existing choices that much more viable.
I saw an article here about how Game Maker should consider C2 as competition, and I agree. I also think, though, that C2's rise doesn't hint at Game Maker's fall. If anything it speaks to a growing community of indie developers using a variety of tools, all of which serve a purpose. I'm not going to specifically advertise my favorite game engines or go into why I like them, but I'll say that C2 is at the top of my list.