WordPress’s Legal and Policy Manager at Automattic (2013-present) Jenny Zhu, clears up the concern you have about if you own your content that you publish on your WordPress.com or self-hosted WordPress.org blog:

“You own all content you post to your website.”

If you ever wish to migrate from WordPress.com to a self-hosted version of WordPress to gain more control and power over your website, you can easily export your content from WordPress.com and import into your new self-hosted WordPress.