I believe the textbox controls are being used in the new taxonomy interface.If you want to find them the wrappers are all in the source solution in the DotnetNuke.Web project, in the UI/Webcontrols folder. 

A quick search shows DNNTabStrip in use

DNNTreeView

DNNWindowManager

that's just with a quick search through that folder and references to those controls

The new Taxonomy and Messaghing modules use a number of Telerik controls.

There is a DnnGrid which wraps the RadGrid, a DnnCombo which wraps the RadCombo.

In Taxonomy there is a control which wraps a telerik TreeView and ListBox and displays the appropriate mode depending on whether the Vocabulary is defined to be heirarchical (tree) or simple (list)

In addition the Tag/Category selector in manageTabs and modulesettings is a custom control which includes a Telerik TreeView inside a Telerix Combo to provide a drop-down treeview control

There is a whole new set of server controls in the DotNetNuke.Web project in the DotNetNuke.Web.UI.WebControls namespace, some of which are telerik wrappers and some are just new web controls.