Actually BioWare themselves have stated long ago that they have all the important voice actors on their beck and call, for whenever they need, they have all of them on contract, much like they do with the majority of their franchises.
I don't mean to rain on the parade -- like you guys, I'm eagerly awaiting this feature -- but in the interests of not relying on false assumptions, the above is incorrect. I've worked in the animation industry, know a lot of voice actors, and none of them work for free, or can be called back for additional recordings without additional payment. If all the SGR material was performed and banked before launch and is just sitting on a HD at BioWare, waiting to be animated, that's one thing. But if they've assigned it to a writer, that means new recording sessions. Which means booking studios, engineers, and actors, the latter of whom are not contract players, but are paid on a per session basis. So in order to implement this feature, BW or EA or whomever is responsible will have to spend money.
Personally, I think it's worth the cost -- much more than whatever they're budgeting to increase the level cap. Hard core players will burn through the new levels pretty quickly and then likely start complaining about a lack of high level content again, but people who are interested in SGRs will reroll a class (even if they already have a level 50 and have completed the class storyline) and play the whole thing all over again from level 1 simply in order to experience that element. At any rate, I know I will.
But we should acknowledge that this does represent an additional expense at a time of corporate belt-tightening -- especially at BW -- and hope the fact that this subject has exceeded the thread capacity so often will remind them how important this feature is to a large percentage of their most enthusiastic customers.