Thief Go, Deus Ex Go, Life is Strange Go, and Just Cause Go have all been registered. This suggests that Square Enix plans on creating more puzzle games for their other IP’s.
The original discoverer, a Neogaf user, was the first person to spot the registrations. He points out as well that the domain registration follows the same pattern established by the past Go games.
Domain registration doesn’t exactly mean that the games will all be made. Square Enix hasn’t confirmed the existence of the games or even that they’re in pre-production. It could be just to reserve them in case they plan on developing the titles in the future.