If this happens it means that the Space Launch System rocket was not canceled and another $20 plus billion was spent on an outdated and expensive rocket. It also means that a space station would be built for tens of billions of dollars that does not rotate to simulate gravity and which has an internal volume several times less than a SpaceX Starship.
The NASA 2019 justification for the gateway and SLS is that the Space Launch System (SLS) is designed to evolve to the highest mass and volume capacity rocket ever built. There is no feasible means to redesign it or any other heavy left rocket to more transport the lunar landing elements on a single launch by 2024.
If NASA is still able to say this that would mean that the SpaceX Super Heavy Starship with a fully reusable launch capacity of 100 tons is not flying commercially by 2021 as planned.
The SpaceX Spaceship has a volume of 1000 cubic meters versus the lunar gateway’s planned 125 cubic meters. The SpaceX spaceship has more volume than the 2016 ISS with 931 cubic meters.
Two SpaceX Spaceships could be tethered together and rotated for simulated gravity.
NASA is also justifying the lunar gateway as support and to develop two to three-year missions to Mars. This would also not be needed with the SpaceX Super Heavy Starship. By refueling five or six times, we could have a fully refueled SpaceX Super Heavy Starship at a high earth orbit Lagrange point where it would choose the right time to leave earth orbit with 9-10 meters per second of delta-V to get to Mars in 4-6 months one way. This would be the delta-V that we take off of Earth. Instead of the 2-3 meters per second of delta-V with a final stage Mars mission if we start from Earth without refueling.