Source 2 will be tuned for modders, according to Valve's Newell
 

It's no secret that Valve is working on a next-gen version of its Source engine. Some Source 2 screenshots leaked out about a month ago, and they showed a marked improvement in visual quality—but that's not all that in store, as Valve's Gabe Newell himself revealed during a reddit AMA yesterday.

http://techreport.com/news/26117/sou...o-valve-newell