Вот
gulp.task( "babel", function ( ) {
    return gulp.src( "src/*.js" )
        .pipe( babel() )
        .pipe( gulp.dest("dist/") )
        .pipe(webpack( {} ));
});
gulp.task( 'watch', function() {
    gulp.watch( "src/*.js", [ "babel", "webpack"  ] );
});
gulp.task ( "webpack", function ( ) {
    return gulp.src('dist/*.js')
        .pipe(webpack( {} ))
        .pipe(gulp.dest('dist/'));
} );
gulp.task('default', [ "watch", "babel", "webpack" ] , function() {});