BPML 1.0 enables the modeling of end-to-end processes by leveraging the Web Service Choreography Interface (WSCI) specification developed by BEA, Intalio, SAP and Sun. BPML success or failure, to a large extent, would be dependent upon its ability to reach broad consensus among both vendors and users. This challenge has been a major stumbling block for other standards bodies such as DMA and WfMC, albeit completion of specs and interoperability tests.
Both BPML and BPEL4WS claim to be a super set of XLANG and WSFL (from Microsoft and IBM respectively). At the moment, it seems that BPEL4WS's claim is better supported and it also stands to benefit from support by the respective platform vendors (and also by BEA). BPML 1.0 still does not address two fundamental requirements, namely user interactions and B2B collaborations.
Please also take a look at the answers to the recent questions: "Why does BPEL4WS get so much more attention than BPML?" and "What is Web services choreography?" for additional details on how the various standards relate to each other (under the main answer page.)