I always add value to merchants accepting Bitcoin as payment solution, but it's mostly always through third party payment processors. It would be an amazing first step if they happen to at least accept a small portion of their Bitcoin sales directly. It is an option that is available within the portal of these third party payment processors. I think that's the moment when we will see merchant adoption actually affect the price in a positive manner.
I can't really see that become reality in the coming few years. We have to look at this whole situation from the merchant's side; If they happen to generate $10,000 in Bitcoin sales, and they keep everything in their own wallet, they will be extemely vulnerable to Bitcoin's volatile nature. If the price happens to go down with 15%, which isn't that unlikely to happen in a matter of just 48 or so hours, it would mean that the merchant in question lost $1500 in sales. Merchants need a constant flow of liquidity, and Bitcoin isn't exactly helping in that aspect.