GoNintendo had posted an exclusive interview with Tyrone Rodriguez (Nicalis, producer) and Pixel, although only three questions were really answered by the developer of Cave Story himself. In regards to the topic of remixed music which has been discussed by many, here's what Mr. T has to say about it:

"The WiiWare version of Cave Story features all-new music rearranged by Yann van der Cruyssen. He’s worked with Nicklas (Nygren) in the past and we’ve really liked working with him. We’ve paid very close attention to stay as faithful as possible to the original music. Each track is passed off while in-progress state to Amaya so that he can review and approve it.

Yes, the old music and graphics will both be retained via a switch. You’ll also be able to mix-and-match audio and visuals. So, if you like the old art and new music, or vice versa, you can do it. Cave Story has a huge fanbase, we’re aware of that and want to make sure that it’s true to what they expect and Pixel-approved. If they don’t like the new art or music, we won’t be offended and they can play the game in its original state."

The Cave Story interview - Tyrone Rodriguez and Pixel