Freescale make /lots/ of microcontrollers. I presume you have a family in mind, rather than just looking for any sort of microcontroller made by Freescale and with at least three UARTs? Otherwise I'd recommend the MPC5554 - using the TPUs, you can get a total of 34 UARTs.
Thanks for your replies. To complete the thread, here is the list of microcontrollers having three UARTs. I have included non-Freescale microcontrollers too for anybody who may need a similar search result in the future.
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