There is little doubt that Stalin dying was a great idea: very classy of him to have finally done so. But, as the article itself notes, "The authors state that a cerebral hemorrhage is still the most straightforward explanation for Stalin's death, and that poisoning remains for now a matter of speculation."
To me it is not at all suspicious that his death benefited many people. Of course it did: he was a dangerous and powerful dictator. Similarly his symptoms are very common under natural circumstances; the fact some poisons produce similar symptoms doesn't mean much. And the secrecy surrounding his death is exactly what I would expect even for a nature demise: all of Stalin's underlings and rivals would seek to keep immediate news of the event from the public eye until it could be correctly spun to benefit themselves and to prevent undesired reactions of fear, uncertainty, or rebellion by the population.
Speculation might be interesting in the same way as are crossword puzzles, but at least the latter allow one to confirm one's conclusions by peeking at the key published in the next day's newspaper.
The movie, "The Death of Stalin," was funnier than I had expected and probably at least as accurate as the speculation in the article.