Updated: From very solid sources we can gather that this rumor is mostly false. Close, but not accurate.
Our sources here on Faeit 212 responded with the following
"Those aren't codices. But they are close to what actually will be released. Primaris, as GW said today, aren't their own faction. "
More rumors are out regarding the 5 codexes we will see released for 8th Edition. This one is rated rather high from the Salty Wargaming site, but still consider this a rumor.
Please remember a little salt when digesting rumors.
via Salty Wargaming
http://saltywargaming.blogspot.co.uk/2017/05/warhammer-8th-edition-codex-rumours.html
Codexes of 8th Edition
1) Armies of the Astartes: Adeptus Astartes, Grey Knights, Death Watch, Primaris Astartes.
2) The Imperium: Mechanicum, Inquisition, Adeptus Soritas, Astra Militarum, Imperial Knights, Officio Assassinorum, Adeptus Custodes, Sisters of Silence.
3) Xenos book 1: Eldar, Dark Eldar, Ynnari, Harlequins, Necrons.
4) Xenos book 2: Tau, Orks, Tyranids, Genestealer Cults.
5) Chaos: Chaos Daemons, Chaos Space Marines.