At the ripe old age of twenty, the humble firewall might be considered past its prime by some, but despite the many declarations from various experts that the perimeter is no more, that we live in an age of networks without borders, and that firewalls are antiquated legacy constructs that are no longer relevant, in fact the firewall just keeps evolving to deal with the new and different threatscape.
If you want to know Why the Humble Firewall Still Stands Strong, check out this article:
http://www.information-age.com/technology/security/123458688/why-humble-firewall-still-stands-strong