Re: "Block 4 is said to be already in development"
Of course the next version is already being developed.
Adding Feature P is not reliant on Feature H already being present.
It is very common for large software projects to be simultaneously working on (parts of) the next two or three "important" releases.
Even when it's just one person, there is continual planning for the next version - "I can't fix that now, note it for later" - and partial implementations (eg the most useful 20% of the feature) to be expanded on in a later version.
I think the only exception is games, where there's no intention that there will ever be a next version.
Ignoring the future is stupid.