Gan have been teasing a 5x5x5 for a very long time but there is still no release date yet announced.
For a long time, Gan were known for only producing 3x3x3s, often with an annual flagship that promised to be slightly better than the original. Then in 2018, they released the Gan 249 which did not go down very well in the community but signalled that Gan were going to begin producing puzzles for other events. Later in 2018, they released a 4x4x4 which was seen by most speedcubers as a major flop and is a puzzle that I simply refused to ever stock. In the coming years, Gan released a very good 2x2x2, a very good skewb, a pretty good pyraminx, and even a magnetic mirror cube.
This year Gan released a megaminx which has been plagued by production delays but will hopefully be fully available in the next week or two, Gan's first megaminx was decent but most speedcubers preferred cheaper options such as the YuHu V2M when it was first released, it seems likely that a lot of speedcubers will be switching to the Gan Megaminx V2M once they can get it in their preffered colour scheme.
But the Gan 5x5x5 just seems to keep getting delayed, Gan even teased on April Fools Day that it's release would be cancelled.
Gan also seem to have felt forced to release a Gan 14 Pro which claims to fix some of the issues with the original Gan 14, this would inevitably delay any release of their 5x5x5 as they only have limited production capacity.
However, we know that Tymon Kolasinski has had a Gan 5x5x5 for months now and he claims it to be the best 5x5x5 out there but unfortunately the rest of us will probably have to wait another month or two before we can try this 5x5x5 out for ourselves.