1/ Joomla! 4 stable and ready for production : not that soon ;-)
2/ Joomla! 4 stable + a potentially Seblod 4 stable and ready for production : too far away for having some commercial expectations
I think we have to keep J!3 if we really need Seblod functions or moving to another system / CMS. Event at the current state, the lack of community and support and documentation is pulling down this great tool. Im' not blaming anybody because I know the money and time needed for these projects it's just a facts. Seblod is mainly a CMS in a CMS and have to handle the Joomla! limits at this point Seblod could (must ?) become a stand alone. We don't know the plan for octopoos but it's their baby and expertise so if they move to WP or custom dev (Laravel etc) or a Stand alone Seblod Seblod project will take a bit hit, it's the limit of Seblod (and other J!CCK of course).
"Eager" to revamp ? If it's for a graphic revamp : work hard on the template only ^^ If it's for complete new work mechanism, database etc stay on J!3 or move on because again J4+S4 for production it's not for today.
For my own agency I stay on J!3 for the new year for projects which needs content heavy content type etc and in the same time I look for alternative out of J! because other cck are too light for mid-heavy project even if they have nice features on paper.
Seblod lack of interaction with other extentions for example : J!backend, Elastic search or other Algolia extentions don't have plug-ins for. Ocopoos will say "Because Seblod can do all of that by it self !" Maybe but with a lot of code and time and money and we have no informaton/documentation about Seblod API (And I have kased the question on this same forum). You can't use article link manager of Tyni or JCE for making your users life easier.
Our next project we will try to combine algoliaXT for search (autocomplete yeah ! Easy Facet Yeah ! Ajax search Yeah !), Customs fields for content type and Articleanywhere for making article list. It will not all integrated as a Seblod project but Search modern feature are very asked.