As far as the plot goes, it's that Colours explicitly had Yacker and everyone else leave at the end. Lost World didn't even handwave it - they just appeared and it wasn't mentioned at all. I was perfectly fine with Runners saying the some of the Wisps changed their mind and decided to stay. The thing that makes the Wisps different to any Mario power-ups is that they're only useful in very specific areas. It becomes boring and really breaks the flow. In Colours it wasn't so bad because the levels were designed to take advantage of them, even if doing so did bring you to a complete halt. Using them outside of their designated area is either pointless, suicide or flat-out forbidden by the game. That's not a power-up at all. Lost World made it worse. We can all complain about the gimmicky motion control, but even integration into the levels was much worse. Because you almost never need to to use them, they became silly diversions that had absolutely no place in the game. They were shoehorned in there with zero benefit to the gameplay. If this game is going to use the Wisps, I hope it's either only the white ones or they're more limited in number with greater versatility. If the rocket wisp returns for example, it had better be useable and worthwhile throughout any stage it appears in. Also Iizuka mentioned that you fill the boost gauge either with the Wisps or by defeating enemies, ala Colours. You can even see Sonic burst some out of capsules. This probably means that collecting rings won't fill the gauge, so the boost could be used more sparsely this time around. I'm cool with that. The level snippet we saw is very boost-corridorry though.