Add MouseOver Selection states in the RadRibbonTab control

Decline reason: RibbonView and its elements (including TabControl) are inspired by MS Office products. Since hovering over the selected TabItem in MS Word for example doesn't change its visual appearance it shouldn't in RibbonView as well.
If your project design still requires such appearance then we highly recommend that you edit the Control Template of the TabControl in Telerik.Windows.Controls.RibbonView assembly and add a MultiTrigger Condition (in WPF):
  <MultiTrigger>
                <MultiTrigger.Conditions>
                    <Condition Property="IsMouseOver" Value="True"/>
                    <Condition Property="IsSelected" Value="True"/>
                </MultiTrigger.Conditions>
...
</MultiTrigger>
or add a  <VisualState x:Name="SelectedMouseOver"> to CommonStates VisualStateGroup.