I'm roaming Skyrim right now. I'm on Diplomatic Immunity, though I'm not pursuing the completion of the quest. I'm at Alftand right now, where you get the Elder Scroll. Is it possible to get the Scroll before the main quest? I know you need those Dwemer artifacts, so would I be able to go them and come back to Alftand and get the Elder Scroll before the main quest?

Yes, you can. I found the guy who gives you the quest for the scroll before I started the main quest. It was a little confusing the very first time, since I had no idea why my character was asking this guy I never met before about getting an Elder Scroll.