It is not dying but it had has its peek.
The "best" fanmade animations, songs, etc are from years ago and I see a decrease in pony cosplays and artists on conventions. At certain point I was kinda tired of seeing the mane6 being cosplayed over and over again and last convention I did (last weekend of July), I saw 1 rainbow dash... 1.
Things come and go, so same with bronies. I mean back in 2012 it was not conventional to like my little pony as an adult so we got a hell lot of attention. Now everybody knows about us, no shock effect anymore, etc. So we become one of he many fandoms.
Conclusion both intern and extern the brony community is over it peek. It does not mean it is dying. We are still big and active.
My little pony as concept will probably not die. It has been around for decades and they plan G5. We live in a world that produces remakes of remakes and the mlp formula works. All little girls (or most) go through that annoying horse-phase so the market for horse/pony toys keeps existing. MLP also keeps rolling on the fact that parents played with it as a kid, and then they buy the same for their child. I am now 22 and I might have kids by the time I am 28. By that time we are far into G5. Guess what I will buy for my babies? Nice guess, yes, MLP toys.
So it keeps rolling.
As long you stay active yourself, you have nothing to fear.
Keep going to events, keep drawing, keep rol playing, keep supporting artists, keep being you, keep being a brony.