Well in that case I would get a single 1080 or whatever flagship gpu comes down the line if you plan to wait and spend the money you saved on a nice 144hz 1440p monitor and any other parts you many need.
SLI is not what it once was, SLI support for AAA games in 2016 was terrible or non existent for many games and it looks like that trend is only going to continue. A very small percentage of pc gamers have SLI setups, so most game developers do not see the need to properly optimize their engines for it.