Yes, it could result in a lower end work truck EV (Ford version) and a high-end Rivian based vehicle. As the pricing improves for the skateboard it will move down to the lower cost/higher volume models.Maybe as part of the deal Ford has agreed not to use the skateboard platform for a pickup or SUV which will compete directly with the R1T or R1S, either permanently or for a certain number of years.
I don't think the electric F-150 will really be competing directly with the R1T. One is an ICE vehicle adapted to be an electric vehicle while the other one is a ground-up EV. The F-150 being on an adapted platform won't be optimized for electricity unlike the R1T which will have the benefits of being an EV with a skateboard platform (advantages: battery capacity, range, drivetrain simplicity, etc.).