Those firewalls that allow extend the perimeter. Nowadays, there is a issue with the static perimeter and all is going to change in the next semesters. In my opinion, solutions like Netskope are offering this extended perimeter functionality and they could lead the market.

CDN is not going to help you to avoid DDoS. The main function of a CDN is to deliver content faster. To mitigate the risk of a DDoS you need a Web Application Firewall (WAF). Todays WAF come with CDN capabilities.