They are probably doing two "versions", an Xbox 360/PS3/Wii U version, and a PC/PS4 version, which means there will be some upgrades to the PC version, such as almost guaranteed higher detail models and textures.
Lots of games have come out on multiple platforms which were seriously different, such as PS3 and PS2 or Xbox 360/PS3 and Wii, and the older version has been different (often finished by a different studio) to the "higher end" version.
Given that this will be an early PS4 title, it's almost certain they will be pushing the system as of now, and not realeasing a crappy port of the PS3/360 version.
They will also (probably) be using the PS4 version as the base of the PC version, as it's almost certainly being developed on a straight up PC, which means the PC benefits significantly from this being a PS4 game.
Ignore the PS3/360 element, as it probably won't impact the PC version of the game that much, unless Ubisoft do something completely stupid (which is possible, but I would give them the benefit of the doubt with this particular title).