Why not rev the numbers? "3.5" vs. "3.5 New" feels weird -- is there a particular reason why Anthropic doesn't want to call this 3.6 (or even 3.5.1)?
Also, they still haven't released 3.5 Opus yet, but perhaps 3.5 Haiku is a distillation of that, indicating that it is close.
From a competitive POV, it makes sense that they respond to OpenAI's 4o and o1 without bumping the version to Claude 4.0, which presumably is what they will call their competitor to GPT-5, and probably not release until GPT-5 is out.
I'm a fan of Anthropic, and not of OpenAI, and I like the versioning and competitive comparisons. Sonnet 3.5 still best coder, better than o1, has to hurt, and a highly performant cheap Haiku 3.5 will hit OpenAI in the wallet.