For the time being you can use the following CSS:
    <style>
        a.rfdSelect.rfdSelect_Default {
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
        }
    </style>
ASPX:
        <telerik:RadFormDecorator ID="RadFormDecorator1" runat="server" DecoratedControls="All" RenderMode="Lightweight" />
        <asp:DropDownList ID="Dropdownlist1" runat="server">
            <asp:ListItem Value="" Text="(Not Completed)">
            </asp:ListItem>
            <asp:ListItem Value="2" Text="Equipment Note ttttttttttt tttttttttt tt tt" Selected="true">
            </asp:ListItem>
            <asp:ListItem Value="3" Text="Test">
            </asp:ListItem>
            <asp:ListItem Value="4" Text="Hello">
            </asp:ListItem>
        </asp:DropDownList>