Paganism encompasses many religions as some people already mentioned... There is a theory that paganism isn't as popular now because our society has changed so much . As we have moved from tribal organization of society, first towards feudalism and monarchy and now towards bureaucratic sort of government, so has religion stood some parallel changes such as from paganism towards monotheistic religion with all sort of bureaucratic arrangements of the deities themselves- for example Christianity has god and then Jesus and then all kinds of angels/saints, kind of mirrors our form of government. So going along with this theory, it's inevitable that religions are about to change.
Looking at myself, I claim no religion, so I guess I fall in to those 15% and sometimes I refer to myself as atheist, however when I really think about it, I can't say that I don't believe in any kind of power...A lot of times I will pray to the christian god, and sometimes even go to church, but I disagree with 80% of the things my church (eastern orthodox) teaches...I do agree and like some of the teaching of the christian bible, however only if I can put my own interpretations..
This doesn't count as religion though, religion is supposed to be organized and a community is supposed to exist, that's part of what religion strives to do, is to reinforce society's common beliefs and reinforce society itself, that people aren't all that self interested after all and can cooperate with each other just based on trust and solidarity, not solely because of benefits that can be achieved by cooperation..Technically this kind of reinforcement isn't possible if one doesn't participate in a church or group type of worship, no matter how faithful or spiritual one is. I know people might try to argue that it's possible, maybe through online communities or through family worship I dunno I'm just stating some theories i've heard or studied...
So therefore, I think it's very likely that churches are going to change either gradually or sporadically....we just have yet to see (or not if it doesn't happen in our lifetime)
ETA: wow sorry if i made no sense, it seems like what i wrote is kind of all over the place but i don't have time to try to organize what i'm trying to say or even see if it's coherent.