I will now proceed to elaborate my own thoughts without being eaten alive (hopefully).
I think that the feature should be available in the Store, but only as an optional download, not a mandatory update. No one cried chicken shit over the religious features in The Sims Medieval (or the Christmas and Hanukkah items in the Store). Simply adding the exact same religions/religious features as Medieval would be perfectly fine. EA handled religion very well in Medieval, adding both a religion that believes"the Watcher (God)" is loving and one that believes "the Watcher" is vengeful, or you could choose for your sims not to have a religion.
I myself would not make this download. I was raised a punctual Catholic, attending Sunday mass as much as possible and receiving all my sacraments. I stopped believing in God after the sixth grade, or some time during seventh. I'm not going to go into my opinion of religion as a whole, but I will say that I'd prefer it that my sims stayed without it.
Some would like for their sims to have religion, thus the option should be there. There's a mod for a priest career anyway, so if people really wanted it the modding community has a mod for anything and everything imaginable, because I honestly don't see EA creating religion for The Sims 3 anytime soon.