if it's using sata 2 port, there's no point replacing it with a sata 3 hdd or ssd

It's unknown because there has been no official statement.
It most likely is using Sata 2 because Sata 3 is optimized for SSD. I don't see why they would opt for the more expensive bus controller then opt for HDD.
Like the PS3 putting a SSD in your console is seeing little to no increase in speed.

I read an article on ign that you can replace your hdd for sata3 ssd to load your ps4 games faster

This post was edited by Doom0277 on Aug 29 2014 10:01am

well they could've opt for the HDD cause cheaper since SSD are more expensive

So sata 2 port then

Sata 4

But then why opt for the more expensive bus controller and be all secretive about which one they used? I would lean towards Sata 2 for those reasons bun it's not like Sata 3 isn't backwards compatible.

/edit

Sony also had the option to go with 5ghz network band and didnt I would assume for cost.

This post was edited by ROM on Aug 29 2014 11:19am