If more genes for less arm hair are passed on more frequently after several generations will people have more or less arm hair?

That depends

Explanation:

Just because it says more frequently does not mean that the gene will be in every person's genetics. Some will have less arm hair, others more, or if it is a co-dominate gene then some will have an average amount. Now with that being said, just because someone may not express the phenotype of that particular gene does not mean that they do not carry that gene within their gene pool.