The fandom has always been the same, just that you are starting to see it in a different view.. I honestly can't see any difference. From now and then.
Sure, some people don't like new things. But what was the first thing to ever change the show we love? The Twilicorn.
You bet things will go down, no matter how purehearted the fandom is.
Things change and people prepare for the worst.
After the Twilicorn we got EqG.
That is said to be (half) cannon and it is YET a HUGE change to the series as whole. Humans in the Equestrian world? Will this change everything we know?
OF course people will be against it.
Kids within the fandom?
Umm, there have always been immature and annoying bronies, so don't even bring that point up.