Quoting:

Note: After upgrading to the Beta firmware, the devices won't receive new firmware updates in the future as all the new firmware will use the more secure local communication authentication method.

Currently it's the UK version, but all of your devices suffer from this "local communication security risks".  Are you planning to update the firmware for all of them?  And provide betas for all of them to be rolled back?

If some day you find a *real* security issue how will the beta firmware users be informed of the risk, and how will you update their beta firmware?

Will it be possible to install this beta on newly purchased devices?

How will new customers discover the alternate beta firmware and request it be installed?  Are you abandoning 3rd party integration support for future customers?

A better solution would be to make this an option that could be enabled in the firmware with the same warnings you have here.  Do you really believe that the biggest risk to customers with have poor network security and weak network passwords is that someone will gain control their light switches and plugs?
 

This doesn't seem to be a coherent plan making it impossible to recommend the purchase of TP Link / Kasa devices.  Currently your competition, Belkin WeMo, still provides local LAN control without any unnecessary security restrictions.