After the Povetkin series 90% of us knew that it wasn't likely to happen. It's possible he could win a vacant title at some point in the future but I wouldn't bet on it. He'll probably stick around for a couple more paydays before calling it quits, he doesn't have the chin to be a gatekeeper.
He will never win a world title but he will be in a few more entertaining fights. He has good power and a glass jaw so his fights will usually be entertaining. He will fill the old David Price roll for Eddie and Matchroom.
There are way too many belts. If he hangs long enough and one of the top guys leave a belt vacant he could pick it up. He couldn't beat AJ or Fury, but I think he beats Charles Martin, Stiverne, Lucas Browne, Povetkin, Ruiz Jr, Parker... all recent champions. And he already beat a few of these guys. Dillian just needs to play his cards right and capture a peripheral belt so it positions against a big name for a last payday
Professional or not. It's not very professional to be fail a drug test TWICE. A normal fla would fail it once. He's so thick he got caught twice
Only in a freak situation like Jermain Taylor getting a belt way past prime. But he's never going to be top 5 again, which might be the better question.