I know it sounds ludicrous, but I'm now hearing rumors that for a future Star Wars DVD re-release, George Lucas will redub all of James Earl Jones dialogue with the voice of Hayden Christensen for "continuity" (there was also word of Hayden being Vader's voice in ROTS).
I don't think even George Lucas is that dumb, yet, it's easy to imagine him considering it.
Although real fans know that Vader just isn't Vader without James Earl Jones' voice (no disrespect to David Prowse intended).