Yes, you can still buy a MX64W license.
From https://meraki.cisco.com/meraki-support/policies/#product-end-of-life-eol-policy
"The device-specific licenses corresponding to discontinued hardware products will be available for purchase after the EOS Date, unless the license(s) is/are listed in the “End-of-Life Products” list provided below."
The only hardware licenses no longer for sale are the MS22/42
https://documentation.meraki.com/General_Administration/Other_Topics/Meraki_End-of-Life_(EOL)_Produc...
