Here’s short overview of ReSharper 4.5 features and improvements to expect:

• Better ReSharper performance and less memory usage (this is really important, since Visual Studio 2008 runs as a 32 bit process and is not capable of leveraging more than 3 Gb of RAM).
• Improved Solution-Wide analysis that allows to identify:
  • Unused code – marking class members that are not used anywhere in the code.
  • Excessive usage rights – marking class members that could have less visibility (i.e.: protected instead of the public or private instead of the protected).
  • Overly specific types – marking type references that could be made more generic.
• Better support for Visual Basic and full support for VB9 constructs including anonymous functions and XML literals.
• New refactorings for solution-wide transformations.
• Improved support for the naming conventions that will be supported by all R# features.
• New Visual Build feature to display build process inside Visual Studio in a better way and lay foundation for build optimizations in the future.
• Better support for plug-ins (think of it like Firefox Add-ons support with the auto-update capabilities)

Release

ReSharper 4.5 is planned to be released on Q1 2009, while the nightly builds (Early Access Program) were promised by the end of this year.

Upgrade for 4.0 users will be free.

PS: Probably changes in Solution-Wide analysis will come with even more design by contract options to improve development experience by annotating your code.