Recently Razer published a firmware update for the HyperPolling Dongle that enables 8kHz polling rate on all supported mice.
Razer HyperPolling Wireless Dongle | RC30-04410 Support & FAQs
The version in question is 2.00.02.
However, when accessing the support page, the download link actually downloads a much older version, 1.00.00_r9 to be precise.
Razer, please fix this.