That seems to be the consensus. Valve has updated their mapping toolset named Hammer. It's used to create maps in Source, but a recent update looks like it's now ready for Source 2.
There are many little hints that lead you to believe that the resources for DOTA 2 in the new Hammer update have been updated for Source 2. Hammer also has support for new file types that are different from Source 1. Some shared DLLs (dynamic linking libraries) now have a 2 next to it so there are two versions.
While it's common knowledge that Valve has been working on its next iteration of the Source engine, we might be seeing the rendered be released to the public and this could be another step closer to the release of..... no I won't say it.