With 7.9, shaping (read: bandwidth rate limiting) no longer tops out at 4 Gbps. PF could always process/transfer beyond 4 Gbps, presuming you had fast enough hardware to handle such bandwidth. The discussed limit was specific only to queues, when using such to shape traffic.

If you're asking about OpenBSD/PF's general network performance, it is finally performing acceptably since a couple of years back. You can easily saturate a 2.5 GbE interface with low-end hardware.