I don't know about soft openings, but the last rumors I've heard (which was a while ago) sound like Disney's planning for the show to start no earlier than the beginning of May, and possibly as late as Memorial Day weekend. The viewing area is still behind walls right now, so I think it'll be a while. (If it's any time before about June 21st, it is still technically Spring 2010.

)
However, I've seen video of some pretty cool tests being run of the fountains and screens--some even taken during park hours! So you never know what you might see.