DAS, CEP and ML have not been completely merged into the Stream Processor.
In DAS, the real time analytics were handled by Siddhi and the batch analytics were done through Spark. However, in Stream Processor, only Siddhi acts as the core processor and Spark is not used.
Stream processor processes data in streaming manner through siddhi. In order to fulfill the requiremnts for batch analytics, incremental processing[1] which has been introduced to Siddhi 4.0.0 can be used.
Also ML support is provided through ml extentions written for Siddhi 4.0.0.
In das/cep it is required to define several artifacts like receivers, execution plans, publishers etc.. in order to create a analytic work flow.
But in Stream Processor,it is possible to define the whole flow in a single Siddhi-App.
For further clarification, please refer to the DAS to SP migration guide[2] and WSO2 analytics site[3].
[1] https://wso2.github.io/siddhi/documentation/siddhi-4.0/#incremental-aggregation
[2] https://docs.wso2.com/display/SP4xx/Upgrading+from+a+Previous+Release
[3] https://wso2.com/analytics