OpenGL

"WebGL is based on the OpenGL ES 2.0 specification, and retains the semantics of OpenGL ES in order to maximize portability to mobile devices. There are some significant differences in behavior of similar APIs between OpenGL ES 2.0 and the OpenGL API on desktop systems. Many OpenGL programmers are familiar with the semantics on the desktop, and may not know about these differences in behavior. We highlight them here for clarity."

~Khronos

Will there be by any Chances that Construct 2 (or 3) will have an OpenGL renderer for Desktop Exports?

No - OpenGL rendering is only a small fraction of the amount of code that would need to be ported. I'd also add there would be no performance difference in rendering in a native engine, because WebGL already makes the same calls a native app would. See this blog for more information.

thanks ashley!