If retail do not adopt BTC then what the hell are you gonna spend your satoshi's on? Nothing, because they would not be accepted by anyone.
As for price correlation, this is simple supply and demand with more BTC spending going on then the new adopters whomm see retailers using the product will need to convert fiat to BTC. I believe the expanding demand would outstrip the already circulating, actually linited, BTC hence the medium to long term would push BTC prices up.
In fact, previously, a new retailer accepting BTC was taken as positive news and there used to be a spike in the price of bitcoin.
This is no longer the case now a days, with the BTC price remaining stable.
It doesn't mean it's going to stay that way people just didn't see getting Bitcoin would of paid off for them to spend at such sites like Dell if there are a little more important retailers accepting then the price should go up.