It all depends on what is being offered on the market and the quality of the merchants. If it's good stuff (or rather, good bad stuff) people will be willing to pay a premium over the fiat value and we'll see the price rise.

Don't expect any rapid rises, because most of the spent coins are going to end up right back on the exchanges for approximately what the product seller was planning to get for them. But he'll be willing to accept a little more  , and that will happen if we have a lot of people looking to use a limited number of coins.

But if the market fills up with crap and scammers, we're going to have to figure out a way to address that before we see any big run-ups. We're also going to have to deal with a lot of bad press once some fatal heroin is sold and the terrorists, human traffickers and child abusers discover Shadow and it makes the news. I don't foresee many legitimate businesses publicly accepting SDC for that reason, but there is a lot of business to be conducted and money to be made without them.