Hello Ninja,
it is not mentioned for Joomla! 4, but you should prominently inform your customers in your product descriptions, that they buy a dead horse. It will die on 17.08.2023, because you decided to not make it Joomla! 4 compatible. Your new Ad Agency customers have the right to know, that they are led into a dead end, if they buy your component.
You should come clean to your customers if you continue to sell this component. The only alternative for this approach is to make the component Joomla! 4 compatible! Otherwise, it would be misleading to continue selling this component if it is not clearly stated that it will become useless on 17.08.2023.
So please tell your business leaders that it is in their best interest to continue to develop the component beyond 2023 and to continually adapt it to new Joomla! versions! That's the definition of a software company, isn't it?
With kind regards
Peter