As Imp notices, Jack Layton is no longer "ruling out" whipping the New Democrat caucus over the final vote on Bill C-391. Hardly definitive language, but encouraging. Now that the NDP no longer has dissident Liberal MPs to hide behind, the hot potato lands in their lap, and I think they will look awful (at least to the progressive voters they share with the Libs.) if they allow Harper and Co. to pass this measure.
Which is why I think Iggy's laying the discipline on his own gang is good politics, even if the registry is repealed in the end. And even if you're a gun registry opponent that otherwise supports the LPoC: I mean, personal feelings aside, why would you not want somebody else to take the blame for its demise?