I'll most likely get Nintendo's next console because I'm a huge fan of many of their first party games and I'll be excited to see Nintendo finally go HD.
As for the other consoles, it depends. I primarily got my PS3 for Rock Band 2, Guitar Hero: World Tour, LittleBigPlanet, and the Blu-ray functionality. If a next gen console has a clear advantage when it comes to music games then that will weigh heavily into my purchasing decision.
Frankly, I've got so much money tied up in my current gen consoles that it's a bit painful to think about what will come next. I'm hoping that the next gen consoles won't hit for at least 3-4 more years. I think that the current gen still has a lot of untapped potential so it's possible. The Wii would benefit from a hardware revision that adds a hard drive but other than that, I think that the current gen has a lot more to offer yet.
