As of today, it is observed that up to 6 confirmations are needed in most of the places to verify that the transaction is complete. Assuming that it takes 10 mins for one confirmation, it takes up to 1 hour for 6 confirmation. This is really long time. People want real time transactions and would be reluctant to wait for such a long time. Can it become blocker for bitcoin adoption?
To answer the question today, It really depends on the confidence level of Bitcoin's image in the business' eyes. To answer the question for the future, it's very possible that "things" built on top of the Bitcoin network will help solve this problem. Not necessary reduce the time it takes to get confirmations but instead to minimize the risk of NOT waiting for 6 confirmations. If you think about it with credit cards, businesses today completely ignore the risk with credit card charge backs and simply ship items as soon as the buyer has paid even though the buyer can issue a charge back days after the purchase.