“Cannot sin” is misleading, as none of God’s creatures will ever be deprived of free will. But they will be so settled into the truth that they will never again make the choice to transgress the divine law.
M.L. Andreasen was by no means the first Adventist to articulate the contours of Last Generation Theology. Such early Adventist thought leaders as Joseph Bates, Stephen Haskell, D.T. Bordeau, W.W. Prescott, and James White (in addition to Ellen White, of course) also taught this concept in depth, as the late Herbert Douglass has documented in his book Why Jesus Waits.