Multi-GPU has always been one of those topics that I think received way too much attention in the press versus its real-world applications. In theory, it' a good idea to add a second GPU to achieve more graphics performance but in reality the performance scaling wasn't that good and there were usually a bunch of issues that made it a less than pleasant experience.
With the launch of the Radeon RX 5700 series, AMD officially killed its CrossFire multi-GPU technology. In an interview with PCGamesN, AMD’s Sasa Marinkovic explains the company's data showed less than 1 percent of PC gamers are doing multi-GPU configurations.
“I think the latest numbers that I’ve seen is that less than 1% of people are doing multi-GPU configurations,” AMD’s Sasa Marinkovic tells me ahead of the Navi launch, “because obviously, a single GPU is still much better performing than getting the diminishing returns of multi GPU.”
Multi-GPU support is still possible via DirectX 12 or Vulkan, but this will be the job of the game developer.