> Historically, working hours are decreased with increase of productivity. 10-16 hours working days 6 days a week was common just few centuries ago.
Those long days arose in consequence of the industrial revolution (both because the things which enabled them were products of the industrial revolution, and because they were adopted to maximize the return of the capital investments in factories in industrialization), working hours were shorter previously.
Its true that they later came down as a result of social movements spurred by the conditions those long hours produced, but its not clear that those were net shorter hours from productivity or just a reversion of the increase.
(In some areas of the developed world, there've been further reductions since, which may be a continuation of the same social movement adapting to changes in the production capacity, which would perhaps illustrate a socially-mediated course for the trend you suggest, but that hasn't been universal.)