I mean we know Valve has a Half-Life 3 cabal with ~40 members. Valve using an internal working title of Half-Life 3 to refer to something other than Half-Life 3 would be patently stupid.
Well it wouldn't be the first time someone got access to their jira tracker and leaked everything. Also it isn't against Valve to toy with their overly eager fanbase at every opportunity possible.
Time will tell.
It's actually Ricochet 2.
This is a high possibility.