I think any of those three could win a Masters this year - Thiem at one of the clay tournaments, Dimi as soon as IW or Miami. I don't see Zverev being quite ready, but maybe later this year, after Wimbledon.
That said, my article was focused on how to differentiate future greats, or at least elites, from future second tier players. Who becomes Rafa and who becomes Gasquet? The one commonality among the greats that I found is the short gap of time - within a calendar year - between first title and big title (by "within a calendar year" this could be in January of one year, and November of the next). As said, the only exception to this among 6+ Slam winners in the Open Era was Agassi.
But Dimitrov and Thiem already "failed" this benchmark, as Dimitrov won his first title in 2014, Thiem in 2015, and neither followed up with a big title in the next year. In terms of historical precedents, their best-case scenario are becoming multi-Slam winners, but not true greats.