The NDP really doesn't have a leg to stand on, let alone to throw their weight around. If they topple the government and force another election anytime soon, the electorate will absolutely stomp on them.
When faced with an existential threat, humans do not do the foundational things that prevent those threats from returning. They tackle the facade. Trying to be threatening to stability while everyone feels so deeply threatened and unstable is more likely to destroy the party than to accomplish anything, no matter how good an idea they may want to push.
Plus, the BQ has already thrown their support behind Carney.
The NDP needs to get their house in order, and actually build support by being active members of the community again, and not just the milquetoast social democrat political party with no media outlet backing them.