Short answer…probably not yet. We only say this based on our testing. We used a Joomla 3.10.4 site and downloaded the lastest upgrade package from the Joomla website. We are running a Gantry 5 Template on the site, and a bunch of extensions. None of the extensions are crazy. Mainly Akeeba and No-Number/Regular Labs products. We ran the update and the site was broken.
In the browser title was:
Error: 0 Class 'JRequest' not found
We were hoping it just worked, but we have tried this in past and got roughly the same result. We like using Joomla for the Access Control Levels and the way Joomla handles media such as images over WordPress. Joomla 3.10.x will be around for a few more years; however, we were hoping to go to Joomla 4 for the over all enhancements. Perhaps using a simpler template would work better. For now we would suggest holding off on just upgrading your Joomla 3.X site to 4.
Let us know if this helped you….