I don't think so. The reason that I would use a RAID card with HDDs is to get the benefit of a battery backed write cache, optimally performing RAID operations

I don't think so. The reason that I would use a RAID card with HDDs is to get the benefit of a battery backed write cache, optimally performing RAID operations. I've only seen one RAID card that supports connecting to NVMe drives. It is terribly expensive and aimed supporting the speed of flash-based NVMe drives. If you want a battery backed write cache with flash-based NVMe, get an enterprise drive with power loss protection, and you are golden. You don't generally need the write cache to get reasonable throughput, but you can save a few microseconds in write latency. I suspect that NVMe HDDs will have the same amount of write cache that existing SATA/SAS HDDs have. If you feel you need a RAID card for RAID and/or cache with SAS or SATA HDDs, you will probably have the same need for a RAID card with NVMe HDDs. Both Intel and AMD support limited hardware RAID for NVMe natively on some of their CPUs. I don't think this has any of the cache benefits you normally have with a RAID card. That is, it may work well with flash-based NVMe drives, particularly those with power loss protection. But really, if I'm using hard drives, I'd probably use ZFS with flash-based read and write cache or Storage Spaces with a flash tier and its integrated write cache on flash.