I think its a toss up.. At some point, I highly doubt you'll need SLI. I have a card coming later today that has four hdmi ports on the back of it and supports three screens ( for one picture ). SLI was a step in the right direction, but i think its days are numbered.. NVidia has other plans..
Currently, the second most powerful supercomputer in the world (Titan ) uses all NVidia GPU's to accelerate processing. What this says, is that computing is on the doorstep of entering a completely new realm that will make the computers we have now days about as obsolete as a horse and buggy. I wont speculate on the science fiction world of tommorrow with this new technology, but it's going to be able to encompass everything we do now, and a whole lot more, from our desks at home, including our games..
For some this will be a sad thing. For others it'll be another step into the future ( imagine your taxes done in five seconds ).
Think about it.. This thing below is using Graphics cards to deliver 13.7 petaflops ( billions of calculations per second ) of performance..
