Transaction fees will be one factor, and are already built in. Pay a transaction fee and your transaction gets processed faster.

But also, miners who can't be profitable anymore will drop out. As they do, the mining difficulty will decrease until mining becomes viable again. On the other hand, the first special purpose mining ASICs are starting to be offered, and people with those will be able to mine more efficiently.

I'm not expecting the bitcoin price to change significantly, since I figure it's determined more by the demand for bitcoins than by production costs. Looking forward to seeing whether that's correct.