Intel and NVIDIA haven't said anything official about SLI support on upcomming P55 motherboards, however motherboard manufacturer J&W seems to have brought forth some confirmation of their own.
Just like the X58 motherboards, the P55 motherboards will not have an NVIDIA chip, however board makers will be paying a per-board fee for the SLI license. J&W is showcasing their P55 motherboard. While it looks similar to many other P55 based motherboards, it does have one difference. It bears the NVIDIA SLI logo on the motherboard.
On top support for dual NVIDIA GPUs, the board will also support CrossFireX ensuring that ATI is not left out of the mix. J&W's board has four DDR3 DIMM slots, 8 SATA 3.0 ports, Gigabit LAN, and more. There was no word on pricing or availability.