Population, and here especially women, could really be a problem. Oftentimes, Europe had more land than people. Plenty of medieval documents exist where people gift large parts of land to the church - but no peasants to work them. That would limit emmigration of mere peasants (those will have to flee).
One thing I could imagine is raids: the Norse in Vinland could raid the continent for women, or they could participate in Viking raids and wars back in Europe and bring back women. As already stated, living in Vinland is rather easy: land is plenty, natural richess allow for a good life, you'd just need a wife.
Another thing to consider is immigration of noble second sons. In Europe, they don't get an inheritance. Taking a ship and a couple of peasants makes them a Jarl in Vinland. And if Leif's policies continue even a rich peasant can go this way. That may be something to bring people over. Say the king of Norway gives each of his bastard sons (it's surprising how many bastard sons higer nobility can produce often without the ability to legalize them properly) a ship and some people and sends him over there - a good future for the son.