I know parallel collections will become available.
What form will these take, and what else are we likely to see?
For the full list, see: Beyond 2.8 - A Roadmap
The main thing seems to be parallel collections. They are drop-in replacement for the scala collections, but the methods are executed in parallel.
From the scala days presentation by Aleksandar Prokopec:
Scala parallel collections that will be introduced in 2.8 reimplement standard collection operations while keeping compatibility with existing Scala collection framework. They also introduce new operations characteristic for parallel algorithms, and a few contracts the programmer should be aware of.
For a good video explanation of parallel collections, see Scala Parallel Collections - Aleksandar Prokopec