For better or for worse. I try to be optimistic and think for better.
For three reasons:
1) Stories tend to become better when they have Spike in them *g*
2) At this point ignoring and completely sidelining him would have been a shame, no matter if the story is going to work out or not.
3) If the story doesn't work out, well, at least he's in company.
4) He's not going to be a werewolf, that's one plus.
I'm also glad that Joss seems at least somewhat concerned that the IDW books will indeed stay canon. It's nice to see that he cares a little about continuity and doesn't plan to disrupt it completely.