We wanted to get into more advanced IntelliPrompt features for the .NET Languages Add-on (such as those you mentioned) and that did involve some very major redesigns of the entire add-on's internals. The redesign we've been working on is in the WPF/Silverlight versions of SyntaxEditor and the .NET Languages Add-on. Key new core pieces of the control itself on those platforms, combined with a new add-on written from scratch to fully adhere to C#/VB specs, have allowed us to implement those things and remain fully extensible for future features like LINQ IntelliPrompt as well.
As for the WinForms SyntaxEditor, it has been mature and stable for a while. To do much more with it, we do need a number of the design improvements we've done when making the WPF/Silverlight version. Our plan for the WinForms SyntaxEditor is to get an updated version out in the next couple months that aligns it and the other WinForms products more like our WPF/Silverlight products, distributed and licensed together, with support for client profile and VS 2010 projects.
Once the WPF/Silverlight versions have all the feature areas covered that are in WinForms now (they are still missing some), we hope to port the newer design there back to WinForms so that all three platforms can enjoy the feature areas we add at the same time.