@Jandre If you think Sonic would help Sony in Japan you're sadly mistaken. Sonic hasn't sold well in Japan for a long time now. The only region were Sonic would boost PS3 sales is Europe, which is the place they need the least help in.
Besides that the Wii is a MUCH better fit for Sega IPs than the PS3. Look at the mediocore sales of Ratchet and Clank. Think Sonic could do better? No chance.
SE or Capcom would be a better fit.