This was a hard question for me. I think that a redesign will come in time because there are many improvements that can be made. But this come with almost everything that comes out these days. Theres always room for improvement. A totally new redesign? Thats asking a bit much but Nintendo did it, and so far its doing well.
I guess for now I will just say leave it alone and keep upgrading the Firmware on it. In a year or so I would want to see a new design but by then the next portable sony product will be on the drawing boards!

Edit: If they were to make a redesign I would love to see them put motion sensors in it!! Like the new PS3 controllers!