I don't think there's a strong correlation between tourist numbers and the exchange rate - I imagine that the demand for yen and dollars to import and export goods and also to gamble invest in Forex dwarfs the demand for the two currencies from tourists. And I can't see mom and pop shops in most of Japan gaining any benefit - how many foreign tourists do you see in Kawasaki or Saga or in Nerima-ku, my bit of Tokyo?
You might also be careful for what you wish for. Companies are notorious for using an excuse of increased costs to raise their prices but then do not reduce them when those costs fall. I remember a few years ago an apologetic letter from the swimming pool where my son had his swimming lessons, saying that they'd had to increase the prices because oil had gone up to over $100 a barrel. However, there was no corresponding reduction when the price crashed to about $30 a barrel the following year.
If the dollar strengthens, it will be used as a reason to put up prices, which will remain permanently higher even when the dollar inevitably weakens.