Hi,
We did already made changes to prepare for Joomla 4.0.
For example, in the change log for HikaShop 3.2.0:
We migrated from JRequest to JInput for the filtering of data in order to prepare for Joomla 4 and improve the compatibility with the latest versions of PHP 7.
That was actually one of the major issues to support Joomla 4.0 for HikaShop as it touches a lot of things in the inner workings of HikaShop.
Now of course, if you try to install the current version of HikaShop on the Alpha of Joomla 4, it won't work.
We've done some tests and were able to have a HikaShop running on the Alpha quite easily though.
So we're waiting a bit that Joomla 4 is a bit more finalized before working on it actively.
The Alphas are not yet stable enough for that. We'll work on that with the Betas of Joomla 4.