Hey @Eldar,
Im not 100% sure yet possibly early July, but I do know the testing phase will last about 6 to 8 weeks.
I hope so, Blocs 3 will use Bootstrap 4 so there will be the option to upgrade the project file to Blocs version 3 if its an older one (2.5, 2.6, 2.7), Blocs 3 files wont work in Blocs 2.