Previously from the same source.
http://natfka.blogspot.com/2016/07/40k-8th-edition-campaigns-exciting-look.html?m=1
And here
http://natfka.blogspot.com/2016/07/8th-edition-campaigns-regarding-ad-mech.html?m=1
Via anonymous sources on Faeit 212
I've asked my sources about some things. Both agree that ad mech and Astra militarum will be the Imperial forces in Campaign 3, also Necrons only come in in the last part of the 3rd Campaign the mainstay of that campaign is still about Nids Vs Orks and some Imperial interactions.
One source says that sisters will have their role in Campaign 2 (EOT) but the other has no idea what role they play at all, but both seem to agree that if they are in the campaign it will be as a pre-established army (i.e they will not be getting new releases during the campaign, either they will already have them or they will come after)
Also I asked about the upcoming deathwatch vs harlequins and war zone Fenris, the response I got was:
"In both cases expect some story progression but there will still be some major questions left unanswered at the end of each one as these will set the scene for the 8th edition Campaigns, think of it as being like the recent Tau books where the Tau officially 'won' but 3 problems were left unsolved:
1. The isolation due to the gulf being set on fire (the need to develop warp travel)
2. Tau itself is only just a little way away from Imperial reach and being bombed
3. The whole Ethereal problem due to AunVas assassination and shadowsun becoming more friendly with Farsight.
All three of these questions will apparently be used to form the basis of the Tau Campaign and the same will be true for each respective faction for example Eldar with Warzone Valedor and the upcoming Deathwatch release."