Now see if you can get that same scaling in oh... the other 99% of games?
Running here EVGA GeForce GTX 980 Ti FTW in SLI, and so at 4K resolution (3840x2160px).
I'm getting results at or slightly higher levels that a single Titan X Pascal (all games set at ultra/highest gfx settings):
Firestrike Ultra (DX11) --- Titan X Pascal=~6700pts ; 2 x 980 Ti FTW=~7600pts
Alien Isolation (DX11) --- Titan X Pascal=~112fps ; 2 x 980 Ti FTW = ~121fps (80-140fps)
Thief (DX11) --- Titan X Pascal=~ 62fps ; 2 x 980 Ti FTW = ~ 92fps (89-110fps)
Hitman --- Titan X Pascal=~ 60fps (DX12); 2 x 980 Ti FTW= ~ 74 DX11)
No reason to swap out card.
http://forums.evga.com/980-ti-sli-vs-Titan-X-pascal-m2527021.aspx
If, as you say, a single Pascal Titan X is faster than 2 980Tis in SLI, then I'd be interested in seeing that. I'm sure in games with proper SLI implementation like Mad Max, MGS, etc, 980Ti SLI will come out on top. Here's someone with first hand knowledge who claims this to be the case even @ 4k.