Higher-order corrections for $t{\bar t}$ production at high energies

I present theoretical calculations of $t{\bar t}$ production cross sections through aN$^3$LO in proton-proton collisions. I show that soft-gluon corrections dominate the perturbative expansion not only for LHC energies but also for future collider energies through 100 TeV. Detailed results are presented for various collision energies. The $K$-factors are large and increase slowly with increasing energy. The scale uncertainties decrease greatly as we move to higher perturbative orders.