It's crazy that we can get DLC for tons of titles that don't really need or warrant it, but on the titles where fans clamor for more there is little if nothing offered. It appears we can add Crystal Dynamics' fantastic Tomb Raider reboot to that list. On a recent AMA (ask me anything) thread on Reddit Karl Stewart, Brand Director for Tomb Raider, recently confirmed that there are no plans for any single player DLC for the game. Here's what he said specifically (was asked if there would be any upcoming DLC for the campaign).
We honestly believe that creating a multiplayer experience was and is the right thing to do. This is our very first attempt to create a MP experience and with that comes a lot of learning. We will continue to monitor and tweak the experience until we get it right.
At this time there are no plans for single player DLC
From the subsequent comments it seems that is not going over very well, and personally I have to agree. This game is just dying for additional tombs to explore, but all we'll get is more content for the multiplayer (which has left little to no impression on me from my time with it). It reminds me of how I felt when Arkham City was released. I was looking forward to more missions and story but all I got was one Robin focused side story and more challenge maps. At least with Arkham they delivered some, but compared to the potential such a large playground promised it was a bit of a letdown.
Now, minds can change and plans can be altered, so maybe there will be some down the road. It's just a shame that I don't have more to look forward to in Lara's world, because I quite liked being there.