This is an important bug-fix release related to gulp-style workflows. The stream() method accepts a 'match' option to exclude things such as .map files - this was broken for directories beginning with a . (dot) - this is now fixed in this release, so the following will work as you expect
gulp.task('styles', function () {
return gulp.src('.tmp/scss/**')
.pipe(sourcemaps.init())
.pipe(sass().on('error', x => console.log(x)))
.pipe(sourcemaps.write('./'))
.pipe(gulp.dest('.tmp/css'))
.pipe(browserSync.stream({match: '**/*.css'}));
});