Officially right now if you wanted to use NI serial boards on LabVIEW RT you will need to switch to PXI and if you are going to be using other NI products like DAQ, Motion, IMAQ... I would suggest switching to PXI for its other benefits and you will know that EVERYTHING is going to work. In addition, we are currently looking at officially adding support for desktop ETS to our NI-Serial RT driver.
However, there might be a work around in some instances. In these cases please email in to our customer support for more details.
Joshua Prewitt
National Instruments