Here are my ideas. They're both ultimately up to the RPers of the characters involved, but I thought they would add a bit more excitement.
1. Darkpack, after taking, like, half of Emeraldpack's land (Because I think we're all pretty sure that they're not going to be able to defend it, correct me if I'm wrong), would split up into two seprate packs just because of how big its become. Atra and Nighta would still be leaders of Darkpack, then the second one would be led by completely different wolves. They would either be rivals or allies. That's up to everyone else.
2. The remaining wolves of Pinepack (Mostly mine, which are Splash, Echo, and Fox) would team up with either 1) Meadowpack 2) Riverpack (if wildriverswolf and Silkies agree), or 3)Emeraldpack to try and stop Darkpack. Any ither packs would work, but I'm mainly focusing on the ones that have either had Darkpack steal some of their territory or are really new. This COULD work with the other plot twist as well, they would just have to fight two packs instead of one.
For any of these plans to work, I'd need a pretty general count of the Darkpack members. I don't know how many there are right now, but I think there's enough...