Meh, if Fox did retcon out A3 and A:R, I don't for one second think they wouldn't just put an quick bit of text stating those two movies were in a separate universe or something along those lines and still make a huge box set, which I will still buy again.
I'm not a fan of the retcon, because as much as I think the deaths of Hicks and Newt were handled very poorly, it's still a good movie. I think they should just move on.
Now as far as being concerned about them disrespecting A3 and the people that worked on it? Nada. That production disrespected itself repeatedly and it's a miracle we got the film we did.
If a retcon happens, I won't be happy about that particular, but I don't doubt for a second I won't have a big smile on my face if Hicks and Ripley are on screen. In this day and age and with personal trainers, CGI and makeup, Biehn and Weaver are clearly capable of pulling it off. It wouldn't hurt to go to pass the torch, or just leave them dead either.