The real issue cuts deeper than that. They can record all the new lines they want -- but if they don't revamp the commentary engine, then it won't matter.
I hate to use rhetoric from other OSers, but former OSer Valdarez is/was right when he said that EA's football commentary is event driven. They only react to what's going on in-game. The commentators don't make small talk in between plays a la NBA2K & NFL2k5 -- they're just dead silent after they say their piece.
What's impressive about the NBA2K commentary is how they have the ability to stop mid-sentence to say "Woooooaaaaahhhh" when a dunk is thrown down. To get this level of authenticity would probably involve a total commentary reconstruction on Tiburon's part -- a reconstruction they probably didn't have time for this year.