I was looking at Dark Souls 2: Scholar of the First Sin and I am curious if I would lose my copy of Dark Souls 2 if I upgraded to the DX11 version. Will Scholar of the First Sin also include DLCs, as I bought the Season Pass with the DX9 version of Dark Souls 2.
With all the different versions out there, the publisher made this quite confusing. If you have the DX9 version of the original game with the Season Pass, you can upgrade for 20$, without the Season Pass for 30$.
Scholar of the First Sin (SotFS) is basically a "complete edition" of the game. It includes the base game and all DLC. In addition to that, there will be a patch that adds things like new NPCs and re-balancing that is already included in the SotFS edition, but will be available as a patch for the original game as well.
The benefit of upgrading your DX9 to the DX11 version are improved graphics (obviously), and gameplay changes that are exclusive to the DX11, Xbox One and PS4 version. These include new placement of the enemies (e.g. Heide Knights actually being in Heide's Tower) and more online players in a single session. These changes will not exist in the DX9, Xbox 360 and PS3 versions.
The SotFS edition for DX9, Xbox 360 and PS3 is just the patched original game plus DLC, nothing more. Players of both versions will be playing on the same servers. Players of the DX11, PS4 and One versions will play on different servers, which means you can no longer play with people who have the DX9 version on PC with the new version. You will still keep the original version though.
Here is a table that details the different versions (found on videogamer.com):