https://www.overclock3d.net/news/storage/phison_will_deliver_a_6_500_mb_s_pcie_4_0_ssd_controller_by_q1_of_next_year/1
 
Phison is leading the race when it comes to PCIe 4.0 storage, with their latest E16 controller powering the next-generation of SSDs from Corsair, Galax and Gigabyte, which can already deliver performance levels which can extend read speeds as far as 5,000 MB/s. Phison plans to release a new controller that can deliver speeds of 6,500 MB/s. This is 2x faster than many of the world's leading PCIe 3.0 x4 M.2 SSDs. While the theoretical limit of PCIe 4.0 in a 4x lane solution is around 8 GB/s, the reality of the situation is that these speeds are impossible on the standard. There is a reason why there are no 4 GB/s PCIe 3.0 4x SSDs, or 2GB/s PCIe 3.0 2x SSDs. The same applies to PCIe 4.0.