And other Northern Houses still loyal to the Sarks as an attempt to defeat Ramsey and install Rickon at Winterfell.

I'm hoping that isn't really Shaggydogs head and it just some other wolf.

I suppose the Umbers and other houses could use the Wildling threat as a way to draw the Bolton forces out of Winterfell so that they could defeat them in the open field.

However, it is a risky move and the Umbers have no way of guaranteeing Rickons safety.

Unfortunately, I think the Umbers did turn on Rickon and Rickon will be used as a bait to try to draw Sansa out and then Ramsey will kill Rickon.