I'm not sure I buy this for a few reasons.
1. It is Roger Stone making the claim. He is a BS artist by his own description. If he really was, he wouldn't project it.
2. Assange has said on several occasions he doesn't like Trump either.
3. He is stumping for Jill Stein.
4. He has hinted several times he is also targeting Trump re taxes and Trump foundation.
5. Assange's communication is controlled while he is in protective confinement at the Ecuadorian embassy in London. Not someone you can just pick up the phone and call, even if you have connections.
I think this is either Stone trying to make the campaign part of the story to keep them in the headlines or to somehow sway off any negative release by Wikileaks on Trump.
Trump ally Roger Stone confirmed that he was in communication with Wikileaks founder Julian Assange about the controlled release of hacked Clinton documents.
Speaking on Tuesday to the Southwest Broward Republican Organization, Stone was asked, “With regard to the October surprise, what would be your forecast on that given what Julian Assange has intimated he’s going to do?”...
http://www.mediaite.com/online/trump-ally-roger-stone-claims-to-be-colluding-with-wikileaks-to-torpedo-clintons-campaign/