You can setup auto-update of Scala plugin Nightly builds in IntelliJ IDEA.
Simply select desired update channel from a drop-down menu at "Updates" tab in Scala plugin settings page.

• SCL-9100 Create run configuration for Play pfoject
• SCL-9102 Open in browser after compilation is not working

• SCL-9044 SBT 0.13.9 not working with Intellij

• SCL-9046 Play Framework, Twirl: Syntax highlighting error.
• SCL-9049 Scaladoc generates stub with return also when return type is Unit
• SCL-9051 Cannot rename variable on twirl parameters

• SCL-9015 Very usual situation, when class can't be resolved in evaluate expression
• SCL-9019 A jar dependency (httpcore 4.0.1) keeps being "detached" from its "library" in the IDEA project every time the Gradle project is refreshed

• SCL-8999 Feature needed for call-by-name value parameter error
• SCL-9006 IAE at ScTypePsiTypeBridge$class.create() on Copy of Java type specification with additional bound

• SCL-9004 Interpolation completion is not working for function parameter
• SCL-8944 Update ScalaStyle Version

• SCL-8875 Good code red: weird type inference issues

• SCL-8995 Good Code Red: Cannot resolve method Xxx.Unapply where the unapply method is synthetic but overrides an abstract unapply method
• SCL-8932 Invalid Replace with Option application when body is a function call

• SCL-8579 SBT import does not respect JDK deduced by sbt-structure 1.4.15

• SCL-8965 SBT import is still broken (two months already)

• SCL-8631 Type error not shown when type tooltip is enabled

• SCL-8162 Support Kind Projector

• SCL-8890 inspection access to first/last element by index
• SCL-8917 Breakpoints in lambda sometimes trigger in a different source file
• SCL-8921 Don't truncate the logger message in org.jetbrains.jps.cmdline.BuildMain (line 405?)

• SCL-8935 NPE at autocompletion

• SCL-8920 New SAM inspection doesn't catch Callable
• SCL-5367 Good code shows as red: Using Value Types from Java

• SCL-8157 Good code red: calling apply in implicitly converted object

• SCL-8908 Plugin version lost if switching update channel

• SCL-8793 Good code red: function resolves to a completely unrelated library
• SCL-7170 Good code red: underscore after a by-name parameter
• SCL-7885 Java editor doesn't recognize all exceptions marked with @throws in Scala code

• SCL-4625 Spurious error accessing a protected method within a java class

• IDEA-142373 JavaTestFinders escape

• SCL-8863 Good code red: @uncheckedVariance annotation
• SCL-6140 Support Scala 2.11 SAM

• SCL-8803 Error highlighted when using multiple constructors for covariant generics
• SCL-8632 Import quick fix menu automatically open Exclude sub-menu

• SCL-8760 Wrong documentation is shown in editor
• SCL-8727 Play 2.4 RC2 Routes error highlighted (routesGenerator)

• SCL-8600 <Label>_DebugLabel variables not accessible in Scala debugger

• SCL-8568 Disable "Name boolean parameters" for single argument methods

• SCL-8626 Noinspection ScalaFileName is not working
• SCL-8659 @Nullable parameter annotation in Scala ignored in Java
• SCL-8704 Wrong "Convert match statement to pattern matching anonymous function" suggestion
• SCL-8623 Introduce variable: wrong place is chosen in for statement