gistfile1.js

var gulp = require('gulp');
var concat = require('gulp-concat');
var header = require('gulp-header');
var footer = require('gulp-footer');
var templateCache = require('./template-cache');
var templateCacheWrapper = require('./template-cache-wrapper');

gulp.task('default', function() {
    var templateHeader = "{{ angular }}.module('{{ module }}'{{ standalone }}).run(['$templateCache', function($templateCache) {\n";
    var templateFooter = "}]);\n"

    gulp.src('./templates/*.html')
        // this is my gulp plugin, but it won't work without a header and footer in the concat'ed file
        .pipe(templateCache())
        .pipe(concat("template.js"))
        .pipe(header(templateHeader, {
            angular: 'angular',
            module: 'app',
            standalone: ', []'
        }))
        .pipe(footer(templateFooter))
        .pipe(gulp.dest('./dist/'))
});

// for ease of use, I want to create a wrapper

gulp.task('default', function() {
    gulp.src('./templates/*.html')
        .pipe(templateCacheWrapper())
        .pipe(gulp.dest('./dist/'))
});

(yeah, as you probably can tell, I'm not used to working with streams yet)

The stream you return from your plugin function can be piped to other streams.

Swap

return yourPluginStream

for

return yourPluginStream.pipe(header()).pipe(footer())