The journey to the Wall had largely achieved its purpose. Viserys had obtained Dark Sister, confirmed the existence and threat of the Others to the Night's Watch, and even "gained" a Ygritte, along with the unexpected "wild card" that was Benjen Stark.
He planned to leave Ygritte at the Wall for now, tending to Maester Aemon at Castle Black. With Aemon there, she would certainly be well protected, and she was clever enough to handle the situation herself.
Viserys had told her about this arrangement on their way back to the castle, for he genuinely intended to make Ygritte a bridge between the Night's Watch and the Wildlings. Ygritte herself was willing to do this for the survival of her people, so she willingly put her dream of the south on hold.
As for the Night's Watch, at least the former supporters of House Targaryen and Maester Aemon would support his plan to let the Wildlings cross the Wall and settle in the Gift belonging to the Watch.
After learning what had happened to Benjen, Lord Commander Mormont had also begun to lean toward agreement.
Now the Night's Watch needed only the consent of House Stark in the North to begin putting the plan into action. After all, they still depended on supplies from Winterfell to survive.
House Stark was responsible for the safety of the entire North, and they had no choice but to consider the impact these Wildlings would have. Benjen's outlook had changed after this ordeal, and he intended to go to Winterfell himself to persuade his sister-in-law, Lady Catelyn.
He was very weak now, so the black brothers had removed his bonds, though he was still not allowed to move about freely. With his firsthand testimony, House Stark might relent. Otherwise, Viserys would have to resort