Sony's situation is a bit more straightforward, since their entry-level system is still at $250. Even if the Wii U starts at $300, that's too close. The main thing Sony will need to do is drop the entry-level system to $200.
The other thing Sony has often done is pack software and accessories into a bundle to increase its perceived value. In other times, that might have helped some, but I think this is the wrong time for that approach. For example, if it were to try to bundle its PlayStation Move add-on with every system while keeping hardware prices at their current levels, I'm fairly certain consumers would be uninterested.