Add support for frozen columns. Like in RadGridView or Excel. This way you can scroll the data horizontally while part of the columns are frozen and you can always see them.

When overriden in a derived class the GetAllNames method receives an empty IEnumerable in the "parentGroupNames" parameter.

In the RadPivotGrid:
Open the Label Filter dialog on a dimension, don't set anything and press OK, then all items are present and nothing is filtered out as expected.
Open the Label filter again and manually specify that the value must equal "xyz" and click OK then it will exclude every item that doesn't match this. Again, this behaviour is what you'd expect.
If you then open the dialog, and delete the "xyz" from the textbox so that the dialog appears exactly as it did originally, and click OK then you won't see any items in your pivot grid. This is because it is now filtering out anything that doesn't have an empty string as the label. This is not what I'd expect.
To remedy this, you can click on the dimension and see that the Label filter is still ticked in the context menu, and click "Clear filter", but this isn't exactly intuitive. 
I'd like the filter to be cleared when you clear the text in the box. 

Setting the Expanded property of the GroupsExpandBehavior assigned to the RowGroupsExpandBehavior property of RadPivotGrid to True, and the RowSubTotalsPosition to None, leads to an error. 

To work this around set the RowSubTotalsPosition to Top. 

Or set the IsExpanded property of the corresponding PivotGroupHeader controls manually.

public MainWindow()
{
InitializeComponent();

// the Opacity is used to avoid the flicker that appears because the groups are rendered just before the collapse logic kicks-in.
this.pivotGrid.Opacity = 0;
this.pivotGrid.Loaded += PivotGrid_Loaded;            
}

private void PivotGrid_Loaded(object sender, RoutedEventArgs e)
{
Dispatcher.BeginInvoke(new Action(() => { 
var headers = this.pivotGrid.ChildrenOfType<PivotGroupHeader>();
foreach (var header in headers)
{
header.IsExpanded = false;
}
this.pivotGrid.Opacity = 1;
}), (DispatcherPriority)3);
}

 Create search functionality in the fields section of the RadPivotFieldList. 

Add filtering support for the aggregate descriptions (PropertyAggregateDescription).

Currently, there is such feature for the row and column group descriptions.
https://docs.telerik.com/devtools/wpf/controls/radpivotgrid/features/localdatasourceprovider/filtering

Scheduled for:
The fix for this issue will be included in R1 2019, scheduled for the mid of January 2019. 

Currently it is only possible to either show all or hide all subtotals.

Add support for Hours/Minutes/Seconds steps. Also, add a DayNumber option.

The DistinctValuesLimit property is available in our R1 2018 Release.

add a textbox which allows users to find matching distinc values when using report filters. Very valuable if you are dealing with many distinct values.