The update was delayed too early June as you can see in the official announcement below:
Hello, this is Takaya Imamura, the Director of Steel Diver: Sub Wars. As always, thank you so much for playing. I would like to take a moment to update you on Version 2.0, which we announced recently.
We had been aiming to release Version 2.0 in May. However, we’d now like to ask you for a little more time, in order to ensure that the finished update is as polished as possible.
The current plan is to release the update in early June. I apologise to those who have been looking forward to this release, and thank you for your patience.