I really doubt that the average user will even notice the difference unless they are specifically compairing their screen to another one and looking for a difference. And I would also guess that the majority of people are not sitting around tech forums all day, or even researching their phone online.
Most people just go to the store, play with a few different phones, listen to the sales guy give crappy marketing information and then buy whichever one they think is prettiest and that's that.
So with that in mind, I don't think it will really effect sales all that much, at least not right now. Once they start using the LCD screen and letting people know it might have a small impact but even then I doubt it. Its not like they are going to make a big deal about "downgrading to the LCD", they will just note it as a fact in the specs. The average user won't know or care that there is a difference.
I also think that the majority of people who DO actually care (like many of us here on the forum) are "geeky" enough to have gotten the phone before the switch. Anyone getting it after is not going to be your "OMG, I am Super Tech Nerd and must have the latest/greatest right now!" type of person.
So that's my opinion on the whole thing, based on the fact that in my experience the average people does not know or care about the specifics of the tech world. I would bet that if you went up to 100 random people and asked if they knew the differences between LCD and AMOLED, 95 would say "uhhh... my tv is an LCD... I think, and it's pretty nice. Uhh... what's AMOLED?"