Softbank still owns 90% of ARM and they finished their acquisition of Ampere only a few months ago in November 2025.
I'm a chip designer and a chip this complicated takes about 3 years from start to actual silicon so it would have started well before Softbank started their acquisition process of Ampere.
The press release says it was co-developed with Meta who has a growing custom chip team. Normally these chips like Amazon's Graviton or Google's Axion are designed for their own data center use only and rented to customers. This ARM chip sounds like Meta and other companies will all be able to buy chips for their own data centers.
I'm guessing Softbank will get ARM and Ampere to align on future chips or just merge Ampere completely into ARM.