I personally don't see Jon as the type of person who would stand in his brother's way, even if the North did try to make him their king. As soon as Rickon would be recovered, Jon would likely step aside willingly. I stated in another thread what I see in the northern situation right now. Here's a summary: Bolton holds the North with a very fragile grasp. Manderly, a powerful lord, plots against him. Stannis, an invader, holds a point of power in the North and has persuaded the Mountain Clans, half the Umbers, the Glovers, and finally the Mormonts to join him. Also, Stannis has acquired the Karstark men as well. The Northern lords are angry at the betrayal of Robb, and still wish for independence. Manderly knows, or suspects, Rickon's location and has even sent for him. The Northern Lords could very easily use Stannis to fight Bolton and then depose of him once Winterfell has been re-acquired. This is the likeliest course for the Northern lords to take. If, for some reason, they somehow use Jon as a rally point for continued Northern independence by right of Robb's Will, I don't see Jon standing in the way once Rickon is recovered. You are only partially right... as things stand, the IT does hold the North, but they clearly can't enforce anything and they even have more uprising they're still fighting there.
Robb naming Jon as his heir is just that, Jon is next in line, his heir. Jon's kids would continue after him, there is no taking something from his brothers/cousins, he inherits it all. It's not a bad thing for the Stark kids, rickon could be a knight, etc. I think after all is said a done, the realm and the north will need strong leadership. The stark kids will need that also, and some peace. Jon is perfect!! Besides he is the king, of the north and the targ heir.
Edited by Cinder Stark, 13 February 2013 - 08:00 PM.