I think I’ve found where the confusion occurred.
In your original question you gave the following example:
Example: the tools version of the TextBox class could be named TextBoxXST, or XstTextBox.
I took this to mean that you were proposing an XstTextBox which could be either a WinForms Text Box or a WPF TextBox. Letting logic sort out which was which.
My point was that WPF controls and WinForms controls fall logically into separate namespaces anyway, so what not use them separately. Why bring them together under a single class name?
I would follow what Microsoft did.
Unfortunately there are some controls with the same class name in both WPF and Windows Forms, but since you will probably not mix WinForms and WPF controls in the same window, this should be no major problem.
We will have a xsharp.tools.WPF.xstButton class and a xsharp.tools.windows.forms.xstButton class.