K2 have RTM’ed the 2010 wave support for SharePoint. This is made available as a package which also includes VS.NET 2010 installables. To use this package you need to have the KB1170 installed to your K2 4.5 base.
Also note that there is a video package that helps you get started quickly with K2. It walks you through everything from creating the process to deploying and testing. Here’s more information on it