PCIe bandwidth at its limits?

Hey guys

PCI Express 3.0 seemed like it had a whole lot of bandwidth for anything else we could think of and more. A single PCIe 3.0 x16 slot could deliver up to 128Gbits/s, and on the storage side of things that used to be a lot, so much so that RAID cards like mine (Adaptec 81605zq) only came with an x8 slot to provide direct connection up to 16 drives. At full capacity each SATA 3.0 drive can only provide up to 4Gbps instead of 6Gbps, but that was not too bad.

Now enter the new U.2 (NVMe) form factor for the newest flash drives, each drive directly attaches to a PCIe 3.0 x4 link for a whopping 32Gbps bandwidth (versus 6Gbps from SATA 3), so 4 good drives can in theory saturate a full x16 bus. It seems there cannot be any good RAID controller capable of taking full advantage of the U.2 drives potential.

Enter PCIe 4.0 (coming soon). From news pieces I read it seems to double the bandwidth of PCIe 3.0, so... a newer PCIe 4.0 x16 link would be saturated with 8 good U.2 drives. A 16 drive RAID solution would run at best each drive at half speed.

So... what next? Flash based storage has jumped exponentially in capacity and speed, but the interconnect buses are not keeping up with it. Is there any other solution to feed for example 16 bandwidth hungry U.2 SSD drives besides splitting them in multiple controllers?