Roku is likely to move away from its longtime numerical naming scheme (Roku 1, Roku 2, Roku 3, Roku 4) when the company next updates its product lineup sometime this fall. Instead, according to Zatz Not Funny, the lineup will switch over to names like "Roku Express" and "Roku Premiere" with the next hardware refresh. You can expect to see five models in all, if these new vendor authorizations are accurate.
The Roku 1 will be replaced by the Roku Express and Roku Express Plus, though it's not yet clear what the difference between these two boxes will be. One could offer a slightly faster processor or better remote. The Roku Premiere and Roku Premiere Plus will succeed the existing Roku 2 and Roku 3 models, and both are expected to support 4K video. At present, only the current Roku 4 supports Ultra HD video. The Premiere Plus may also be compatible with HDR video for added dynamic range and a more immersive viewing experience.
Then at the top of the lineup will be the Roku Ultra, the followup to last year's Roku 4. The Ultra will offer a remote locator feature and optical audio output, according to a recent FCC filing, and it too will support HDR streaming.
These new names should make more sense to your average consumer as opposed to "the new Roku 3" and so on. It's easier to tell where each model fits in Roku's lineup this way. Unfortunately, it's not yet known exactly when Roku will launch its latest boxes. The company will definitely want them on shelves well ahead of the holiday shopping season, so you can likely expect to see them within a month or two at most.