Since before Sonic Frontiers even launched, Sega made it abundantly clear that future instalments in the franchise would be building on the foundations laid down by the open world platformer, and with Frontiers having sold as well as it did, it’s safe to assume that the company is probably sticking to those plans. In fact, a direct sequel to Sonic Frontiers seems to be in development.
That’s as per known leaker Daniel Richtman, who has claimed that Sonic Frontiers 2 is in the works. Meanwhile, prominent Sega leaker Midori has also corroborated the leak, though she adds that while the title is a sequel to Sonic Frontiers in terms of its gameplay style and structure, it may not necessarily end up being called Sonic Frontiers 2. The original Frontiers, for instance, was called Sonic Rangers until pretty close to its official announcement.
When Sega might officially announce this remains to be seen, especially with the company having no shortage of Sonic-related releases in the pipeline as it is. Sonic X Shadow Generations is due out sometime this Fall, while the film Sonic the Hedgehog 3 (which will star Keanu Reeves as Shadow the Hedgehog) is set to release this December.