The problem is that you are displaying the form as a Django form.
The rich edit text field will be a JS thing which Django will not create. The django.form feature will be create a HTML element.
I suggest manually putting the rich edit in to the template. As long as you give the rich edit the same "name" as the Django form element you can use it in the POST which is returned.
EDIT: You are publishing a models.TextField() when the form is rendered. This will generate a element in the form. This form will have only default properties.
I am not 100% sure how TinyMCE works but you would need to bind it to that element though a "id" or "name" value or just put the forms code in yourself into the template.
I myself do not use Django to render the forms I create forms myself in the template and give them the same names what Django would give them.
Look at the source code for the rendered page and see what the form looks like. Then set up a test page with TinyMCE and get it working and look at the difference between the element.
:)