This ticket proposes adding new ListSerializer and ListDeserializer classes as well as support for the new classes into the Serdes class. This will allow using List Serde of type Serde<List<Inner>> directly from Consumers, Producers and Streams.
Serde<List<Inner>> serialization and deserialization will be done through repeatedly calling a serializer/deserializer for each entry provided by passed generic Inner's Serde. For example, if you want to create List of Strings serde, then serializer/deserializer of StringSerde will be used to serialize/deserialize each entry in List<String>.
I believe there are many use cases where List Serde could be used. Ex. https://stackoverflow.com/questions/41427174/aggregate-java-objects-in-a-list-with-kafka-streams-dsl-windows, https://stackoverflow.com/questions/46365884/issue-with-arraylist-serde-in-kafka-streams-api
For instance, aggregate grouped (by key) values together in a list to do other subsequent operations on the collection.