No second letter relating to the later-than-expected availability of the improved/remedy blower motor has been sent to owners.
The Supplement #1 notification in the above-linked post -- also included below -- was only sent to dealers...
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If your vehicle's blower motor is currently exhibiting any signs of malfunction, then by all means contact your dealer and they'll install the interim blower motor, and then your vehicle will receive an improved/remedy blower motor once they are available.
If your vehicle's blower motor is working fine, then you can consider contacting your dealer closer to June.
I will be posting an update here when Ford sends their Supplement #2 notice to dealers announcing the improved/remedy blower motor availability along with the ordering process to receive them.
If you click on the "Watch" button and opt to receive e-mail notifications about this discussion thread, then you'll be aware and able to schedule your vehicle into the dealer for the final Safety Recall service action.
Good luck!