I think that a slightly more mature show could appear in the future but as for an adult version of MLP, that's definitely not going to happen. There would be a lot of angry parents if such a thing existed. Just imagine a little girl finding it and thinking that it's just an innocent MLP cartoon, and watches scenes with gore and sex. The reason FIM is so beloved by many is because it is an innocent cartoon with no mature content and it can appeal to anyone, even if they are not a little girl.
I occasionally use everpony when referring to fellow fans but for the most part, I use everybody. When referring to ponies I use everypony, though I have referred to them as everybody. However, I have not and never will use everypony when talking to people who are not fans of MLP.
Nope, bronies are not a type of religion. Just because we follow morals doesn't mean we believe in a religion based on MLP. There are many users on here that have their own religious beliefs and as far as I know, none of them involve ponies.
Twilight would be an atheist or agnostic. Applejack would be a conservative protestant Christian. Fluttershy would be a jainist, Buddhist, or Christian. Pinkie would be a progressive Christian. Rainbow Dash would be an agnostic. Rarity would be Jewish or Catholic.
I consider myself a brony. In the past, I didn't think of myself as one due to my insecurities about liking MLP and the stereotyping of bronies by mainstream society. However, my browser and YouTube history suggests otherwise. So, yes, I'm a brony.