TETHYS_MAP_VIEW.getMap() is the correct form, however you must call it after the page finishes loading. This can be done easily using JQuery (which is automatically included with Tethys apps):
$(document).ready(function() {
var map = TETHYS_MAP_VIEW.getMap();
console.log(map);
});
or equivalently:
$(function() {
var map = TETHYS_MAP_VIEW.getMap();
console.log(map);
});
Sometimes it may be necessary to use the window load event:
$(window).load(function() {
var map = TETHYS_MAP_VIEW.getMap();
console.log(map);
});