Not sure whose interested but basically some file's in SourceFilmMaker confirm that Source 2 is Valve's next-gen engine they are working on.
You can find more discoveries and shit here.
Known engine names
SOURCE = 'Source'
SOURCE2 = 'Source 2'
SFM = 'SFM'
HYBRID = 'Hybrid'
ALL = 'All'
SOURCE_FAMILY = ( SOURCE, SFM )
SOURCE2_FAMILY = ( SOURCE2, HYBRID )
ALL_ENGINES = ( SOURCE,