Sli and Crossfire as we knew them are dead.
Since we got the new consoles devs now have to do much less than they did before. I will elaborate on that a little, then you can make your own mind up.
OK, so with a console like the 360 or PS3 they used hardware that was pretty much completely different to a PC. This meant that they had to do a lot of work creating libraries (portions of code) to make the game work on a PC.
So basically the graphics technology and so on were completely different in the consoles and they had to basically rewrite the graphics and CPU handling. When they were doing that they were also adding in AFR support (alternate frame rendering). There was no point in not putting it in, seeing as you had to do the spade work whether you liked it or not.
AMD and Nvidia were simply giving them instructions on how to do it and they were adding it in. At which point AMD or Nvidia tweak their drivers and you have multi GPU support.
But.
With these new console "ports" (they are anything but) the hardware they are writing for is pretty much a small PC in disguise. I'm generalising here, but I really don't want to pick the peanuts out of the poo on how similar/different they are.
As such devs now don't have to do hardly anything to make that game run on the PC. The consoles use an X86 set up of sorts and this is why Microsoft are now back to releasing PC games because they hardly have to do anything to make them run on a PC. They can almost take a Xbone game, create a PC .exe and run it on a PC.
And that's why you have seen Crossfire and SLi support basically fall off and die. Why would devs waste a single minute of their time or effort rewriting the GPU handling so that people with two cards can benefit?
On the contrary, nearly all of the current games are not AFR friendly. Nvidia and AMD are doing their best, but even with for example Doom Nvidia released a SLi driver for it that actually makes the cards scale negatively and you lose tons of performance over one card and the minimums are quite frankly awful.
Crossfire is even worse. I will use Need for speed as an example but you can pretty much apply this to any modern release. Basically when the game initially launched it stuttered and froze like a sonbitch. AMD released a driver that basically made it worse. Then they released another one that stopped the flickering and stuttering but the scaling was negative and the game ran like poo.
In the end they simply added in a few lines of text into their release notes instructing the user to basically disable Crossfire as it did not work.
This is also why AMD just released the Fury Pro Duo for, quote, "VR development only".
They know that their days are numbered.
In the green camp Nvidia have basically washed their hands of 3-4 way SLi but are still recommending two way SLi. Trust me when I say, it's a con. It simply does not work and hasn't for a long time.
Moving forward...
As I said, Crossfire and SLi are now dead as we knew them. AFR support has been non existent ever since these new consoles came along.
There are a few multi GPU technologies coming, but so far there is only one DX12 game that actually uses it and makes it work and the scaling is pretty bad. Nowhere near as good as a proper AFR title.
Liquid VR supposedly uses more than one GPU also, this is why AMD were keen to push the Fury Pro Duo onto devs. However, what will come of it is a mystery also, because it's too early to say.
So there you go, more than enough info for you to consider and chew on and make your own decision with
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