Dynamic Routing Menu Title

custom.links.menu.yml

customizations.test:
  title: 'My account'
  weight: -10
  route_name: user.page
  menu_name: main

customizations.sample:
  weight: -9
  class: \Drupal\customizations\Plugin\Menu\SampleLink
  menu_name: main
  parent: customizations.test

Drupal 8 Dynamic Menu Title

References

https://www.drupal.org/node/2122201
http://drupal.stackexchange.com/questions/189305/can-we-add-the-destination-query-parameter-to-a-link-from-yml-configuration
https://www.drupal.org/docs/8/api/routing-system/structure-of-routes
https://www.drupal.org/docs/8/api/menu-api/providing-module-defined-menu-links

SampleLink.php

<?php

/**
 * @file
 * Contains \Drupal\customizations\Plugin\Menu\SampleLink.
 */

namespace Drupal\customizations\Plugin\Menu;

use Drupal\Core\Menu\MenuLinkDefault;
use Drupal\Core\Menu\StaticMenuLinkOverridesInterface;
use Drupal\Core\Session\AccountInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Url;

/**
 * Modifies the menu link to add destination.
 */
class SampleLink extends MenuLinkDefault {

  /**
   * The current user.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $currentUser;

  /**
   * Constructs a new LoginLogoutMenuLink.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\Core\Menu\StaticMenuLinkOverridesInterface $static_override
   *   The static override storage.
   * @param \Drupal\Core\Session\AccountInterface $current_user
   *   The current user.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, StaticMenuLinkOverridesInterface $static_override, AccountInterface $current_user) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, $static_override);

    $this->currentUser = $current_user;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
    $configuration, 
    $plugin_id, 
    $plugin_definition, 
    $container->get('menu_link.static.overrides'), 
    $container->get('current_user')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function getTitle() {
    if ($this->currentUser->isAuthenticated()) {
      return $this->t($this->currentUser->getUsername());
    }
    else {
      return $this->t('Log in');
    }
  }

  /**
   * {@inheritdoc}
   */
  public function getRouteName() {
    if ($this->currentUser->isAuthenticated()) {
      return 'entity.user.edit_form';
    }
    else {
      return 'user.login';
    }
  }
  
  public function getUrlObject($title_attribute = TRUE) {
    $userid = $this->currentUser->id();
    return new Url($this->getRouteName(), array('user' => $userid));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCacheContexts() {
    return ['user.roles:authenticated'];
  }

}

Handy snippet. Keep them coming.