Was the prologue of the Fourth Gospel appended decades after the gospel's authorship?

Was the Monarchian Prologue (John 1:1-18) of the Fourth Gospel, traditionally ascribed to John, appended to the gospel decades after the gospel's initial authorship? It seems very likely, especially given the internal considerations of divergent grammar, terminology, and Christology. For example, the only two instances of λογος being applied to Jesus anywhere in the Fourth Gospel occur in the prologue (1:1 and 1:14).