Я не очень догоняю слово "поддерживает".
All plugins between sourcemaps.init() and sourcemaps.write() need to have support for gulp-sourcemaps. You can find a list of such plugins in the wiki.
gulp.task('sass', function() {
return gulp.src('src/css/sass/**/*.{scss,sass}')
.pipe(sourcemaps.init())
.pipe(sass())
.pipe(sass().on("error", notify.onError()))
.pipe(autoprefixer(['last 15 versions', '> 1%', 'ie 8', 'ie 7'], { cascade: true }))
//.pipe(gulpGroup())
.pipe(sourcemaps.write())
.pipe(gulp.dest('src/css'))
.pipe(browserSync.stream());
});