• C++ offers no guaranteed memory safety.
• A fictional safe C++ that would inevitably break backwards compatibility might as well be called Noel++, because it's not the same language anymore.
• If that proposal ever gets implemented (it won't), neither the promise of guaranteed memory safety will hold up, nor any big C++ project will adopt it. Big projects don't adopt the (rollingly defined) so-called modern C++ already, and that is something that is a part of the language proper, standardized, and available via multiple implementations.

would you argue that it’s impossible to write a"hello, world" program in C++

bent as expected

This proposal is just a part of a damage control campaign. No (supposedly doable) implementation will ever see the light of day. Ping me when this is proven wrong.