I don't think it will be so noticeable since they are filming New Moon and Eclipse back to back. Breaking Dawn is going to be hard to shoot with all the CGI they will have to do with Renesmee. I don't know if they are even going to make it at all. Although I hope so.
The way I see it, the only person who apparently needs to look more mature is Taylor, the majority aren't going to age that much in the next five years for it to matter to me. I'll be okay with it. They're just going to have to worry about getting fat and mutilating their body and all that.
True~and about the CGI for Renesmee~maybe they'll need alot when she's born- but, as we know- they cut out alot of scenes from these movies. Maybe they'll skip through so that the age difference for Renesmee grow just requires getting a similar looking child actress at a slightly older age?