This isn't even a question. Even the most conservative courts would probably ignore a full rehearing of Obergefell, but they might entertain allowing individual judges or counties to abstain from partaking in gay weddings (and would certainly side with florists, bakers, and the like). On the other hand, while I am somewhat concerned about Roberts's vote, overturning Roe is a common promise on the right today and the votes could theoretically be there by the end of 2017.
People believed votes actually are to overturn Roe v. Wade in 1992, but it didn't happen.