The next subclass to get the 3.0 rework in Destiny 2 will reportedly be Solar, which will be introduced at the start of season 17 at the end of May 2022, according to a prominent Destiny 2 data miner and the developers themselves.
The team at Bungie has explicitly said that every Light subclass will receive a 3.0 rework during Destiny 2‘s Year Five one after the other until all three are done, at which point the team will “go heads down for a while” as they work on new content. Void got the 3.0 treatment to begin the current season, Season of the Risen, meaning next season has to be either Arc or Solar.
The reworked subclass in season 17 will be Solar, according to Destiny 2 data miner @DestinyTwoLeaks.
The 3.0 rework players experienced for Void saw the subclass options expanded with Aspects and Fragments that unlocked new abilities and perks, plus numerous options for Void grenades. Many players wanted to see the Light classes reworked after these options were introduced as part of the Darkness subclass Stasis when that was added during Beyond Light.
Season 17 should introduce the Solar 3.0 subclass, with new Aspects, Fragments, grenade options, and Super variants. This means that season 18 should be introducing the Arc 3.0 subclass. Bungie has said it does plan to introduce a new Darkness subclass next to Stasis in the future, but not during The Witch Queen expansion.
The current season is set to end on May 24, with season 17 likely to begin a day or two after that.