Please remember that these are rumors. Whether Beasts of War are using the same sources (or are using another rumor site like this one) or their own, we don't know, because they do not say. Assuming they have their own source, lets get down to the rumor.
via Beasts of War
Psychic Powers are random.
Simple dice roll determines which powers you will get out of your codex
Personally, I see this happening, however, just not the way others are reporting it. Now this is mere speculation, but it is logical that if powers are random, that they are not completely random. After all you have to buy each additional power, and I do not see GW making this part random.
What I think will happen, is that there will be a new list of minor psychic powers that are randomly selected at deployment from one of the disciplines and powers from the main rulebook. However you would still get to select your codex powers like normal. Examples of minor powers might be as simple as +1 BS for the unit, or +1 WS. I think these would be in the new rule book collectively for each army.
Here are some of the relevant rumors about psychic powers
-Psychic powers are selected during deployment. (except Grey Knights)
-There will be at least 4+ "Disciplines" of Psychic Powers in the game. (WFB has 8 lores)
-Disciplines seem to fall roughly along the lines of the sects described in the novel "A Thousand Sons" as used by the Heresy-Era chapter.
-Each Discipline will have a "Default" power and a set of others that you will roll for each game.
-Number of rolls you get and the the exact details of which powers you end up with are said to be similar to WFB 8th's power selection mechanic.
-Powers have a "Casting Cost" that is different from the mechanic used in WFB 8th.
-Certain 6th Codices will add additional racial specific Disciplines.
If you are interested in a full compilation of what we know, here is a link
While Beasts of War did not give us anything new, it still brings up the discussion. What do you think of Random Psychic Powers? There could be a lot less of Jaws of the World Wolf, or Living Lightning, but in reality we do not know the complete rules on how psychic powers will be selected. I am hoping that we hear something more definitive on this soon, as I think its the biggest black mark on the 6th edition rumors so far.