According to reports from Samsung's South Korean supply chain, the company remains committed to improving S Pen support on this year's Galaxy Z Fold. Reputedly, the Galaxy Z Fold4 will debut 'Super UTG', a stronger and more scratch-resistant ultra-thin glass than the ones included in the Galaxy Z Fold2 and Galaxy Z Fold3.
https://www.notebookcheck.net/The-Samsung-Galaxy-Z-Fold4-may-feature-a-Super-UTG-display-for-improved-S-Pen-support.608809.0.html