Does a revision to hip resurfacing mean a THR or can another resurfacing be done? If a THR is needed will it be the same quality as if you started with a THR? I don't think metal on metal is standard for THR.
Normal course of events would be revision to total hip replacement, e.g. after wearing out/cup loosening failures. I'm hoping that's at least 15 years or more away!
I believe that in some cases, if it's a femur issue (e.g. collapsed head, fracture) then possible no revision if you're very lucky and recover normally or with a surgical repair.
In case of a femoral neck fracture or other failure on the femur resulting in THR then in some cases the acetabular cup may be retained and a large ball metal THR femur component used (this is sometimes the approach, although not in all cases as I understand (ask surgeons), if the resurfacing procedure can't be completed for some reason due to femoral bone quality/other femur issue).
But in case of it wearing out, it can't just be carved out and replaced due to the bony in-growth, so it's a slightly bigger hole in the acetabulum, and a "first" THR on the femur.