The season trailer suggests that, by the end of the season, all of the rings will be forged and if Sauron hasn't yet forged the one ring, everything else will be in place for him. So I'd expect his threat level to be cranking way up over the next few episodes.
The One is forged in Sauron's own forge in Mount Doom, I doubt that will be changed since it's a pretty important important plot point. Sauron seems a long way off having access to Mount Doom at this point.
Speculation: this season will end with the forging of the Nine, and the fall of Eregion to Adar. Adar captures Sauron and drags him off to Mordor in chains.
Season three: Sauron gains some level of influence over the orcs, perhaps using the Nine (Gandalf uses one of the Three, despite not being an elf). He builds his Mount Doom forge and crafts the One. Only for Mordor to fall to the Numenorians and Sauron to again be dragged off in chains (quickly hiding the One).
Season four: Sauron, in the guise of a prisoner of Adar, gains influence over the death-fearing Al-Pharazon and persuades him to attack Valinor (heaven). Numenor falls.
Season Five: Sauron reforms in Mordor, this time as an armoured giant. Events in this season leads to the Last Alliance, as seen in the Fellowship of the Ring prologue.
Meanwhile, at some point during seasons 3-5, the Stranger leads the halflings to Suzat - The Shire, where they become the true strength of opposition to Sauron.
It's pretty clear that Sauron is the main protagonist in this story.