"Block 5 will be the last major upgrade to the Falcon series, "
We'll see.
Musk reckons SX will spin up the whole BFR programme and be ready for the launch of the first 2 of them to Mars by the end of 2022, a leisurely (by SX standards) 55 months away, replacing the F9 entirely.
That is build (from scratch) a 2 stage 108m long and 9m wide fully reusable orbital vehicle with all cryogenic propellants loaded in the worlds largest CFRP tanks with a new engine design and cycle (in fact FFSC has never been done anywhwere in the USA) whose upper stage will "tail sit" onto the booster stage after decelerating from orbital velocity (loosing around 20x more energy than the per Kg of stage mass than the F9 booster stage) without any major surprises in the design, build or testing phases.
And the factory to make it in.
I wish SX every success but something tells me that like the wings-that-are-not-wings on the BFS there will be what most people would call a "Block 6" (which will be called something else) before BFS is ready to deliver anything to orbit.
It might even be enough to demonstrate actual second stage recovery, although I doubt it.
Biting the hand that feeds IT
