Unless the country is very close to the Netherlands, I doubt it will have much effect.

If someone is willing to spend thousands of dollars to travel to the Netherlands because of marijuana, they are probably pretty into marijuana, and if they are that into it, they are probably using it in their home country anyway, despite it being illegal.

The legal barriers are not hard to work around, and in almost every country it would be easier to get illegal marijuana locally than to arrange travel to the Netherlands.