I think the various LMDh/LMH racers are a shoe-in for either updating various Gr.1 entries, or providing new ones altogether, so I'd imagine that pretty much every car from these classes - perhaps aside from the entries from Glickhaus, Vanwall, and Isotta Fraschini - will come to the series, even if they didn't even win a single round of the WEC. Honestly, I'm at least as excited for more DTM cars to come join the Audi in Gr.2, namely those from Aston Martin, BMW, and Mercedes-AMG. I think the 2024 GT500 trio is highly likely, too.
However, what I'd like to see in addition to both of these potential expansions of Gr.2 and Gr.1 would be a way they could be featured in the Manufacturers Series, where the field is much likelier to be more diverse. After all, if people are always going to pick something like a Group C racer when the race is at Le Mans, I think the idea of expanding these groups suddenly loses a lot of appeal. Or, alternatively, this could be something tacked in the next installment, where a PS5-only title could allow for larger fields and thus multi-class racing, potentially leading to concurrent championships held at the same venues, just like what we see with the WEC/IMSA SSC.
Imagine a round at say, Fuji, where there's both a round for the Gr.3 and Gr.2 cars, or one at Le Mans/Spa-Francorchamps/Daytona Road Course where Gr.1 and Gr.3 cars race alongside each other. If it's necessary, there could even be ghosting between classes, not unlike when you're coming up on a car that's been blue-flagged.