Answer:
What lessons are we to learn from this?
The Hanseatic league, just like the Northern Italian City-States of the Late Middle Ages, are early examples of capitalism: they represent proto-capitalism.
In the cities that belonged to the Hanseatic League, the work of merchants was promoted, and capital accumulation and the profit motive began to develop. However, this does not meant that cooperation was out of place. The merchants cooperated voluntarily because they could get more working in association.
Are there prospects for more merchant leagues in an increasingly globalized economy?
There will always be the prospect for more merchant leagues, because people naturally cooperate if it is in the benefit of all the parties.
In fact, trade unions and economic unions could be seen as a form of merchant league, that are created by states instead of individual merchants.