It depends. We shouldn't forget that merchants accept Bitcoin through third party payment processors who directly, or eventually convert these coins to fiat on the market. If the demand remains strong, it wouldn't really impact the market too much, negatively speaking, but if the market experiences a stagnant period, it might actually suffer to a certain extent. It has all to do with supply and demand, simple basics. Only when merchants will start to actually keep a certain percentage of their sales in Bitcoin, I see the market react positively -- less coins in circulation always helps.