Zeiss is rumored to announce a new Milvus 135mm f/2 Apo Sonnar lens. The older model is currently $400 off - another indication for a potential replacement. The 135mm version was not updated when the new Milvus series were introduced in September last year.
The official announcement of the Zeiss Milvus 135mm f/2 Apo Sonnar lens is rumored for this year and can happen as early as May.
Here is an overview of the current Zeiss Milvus lens line-up: