If more and more retailers will start to accept bitcoin when main economy is still based on FIATS. Then you know what happen? Retailers will start to sell bitcoin for money as they earn it.
It will made bitcoin price go lower. Bitcoin no longer will be investment asset but instead a payment method. I am not sure that everyone here is aware of that. We can lose our coins.
I doubt it. You forget that retailers are people, too. So when more retailers accept Bitcoin, more retailers will be able to buy things form other retailers using Bitcoin. Apart from that, to spend Bitcoin, people need to buy it first. So the only reasonable expectation from increased Bitcoin acceptance is an increase in demand for Bitcoin which will in turn lead to higher prices.