This comes up every time Wikileaks is mentioned, and it is ridiculous every time.
Assange has stated, very clearly, that Russia is not the source and that if they had leaks related to Russia they'd publish them. But they don't. Probably because Wikileaks isn't necessary for Russian leakers: it arose because western newspapers were so reluctant to publish leaked material from western governments. But those same newspapers are desperate to publish anything that makes Russia look bad. So why go via Wikileaks, when you could go directly to the NY Times or the Guardian.
The whole "Wikileaks = Russia" line just comes off as delusional. There's no evidence, it has been explicitly denied, and the supporting arguments are very weak.