Will migrating content types be possible? I have a Drupal 7 site with 40 content types. When Drupal 8 will be released than I would like to migrate these content types.

Would this be possible, or would I have to create this content types from scratch?
I guess the best place to search for upgrade process is UPGRADE.txt file. Here you can find the step-by-step approach to follow in upgrading the site from Drupal 6/7 to Drupal 8.

Drupal 8 core will include a robust data migration API: https://drupal.org/node/2121299, part of the IMP initiative: https://groups.drupal.org/imp . Also you can check the recently updated list of modules that are included in Drupal 8 core: http://blog.merge.nl/2014/01/21/drupal-which-drupal-7-modules-went-into-drupal-core

Few of the links that you check:


Getting your site ready for Drupal 8: http://www.acquia.com/blog/getting-your-site-ready-drupal-8
Drupal 8 - Improved upgrade process: http://www.acquia.com/blog/d8migrate
Converting modules from Drupal 7 to Drupal 8:http://webchick.net/upgrade-modules-d8
Converting 7.x modules to 8.x: https://drupal.org/update/modules/7/8