When do you consider the writing of a theoretical framework to be complete?
Short version: Ask your advisor.



Long answer:

It's hard to answer that, as we neither know your field nor your university. Furthermore, a proposal is not a complete thesis, so there might be also differences because of that, there might even be regulations at your university that a proposal can only have some fixed number of pages.

As you are looking for advice, here is one:
Make a list of all the topics you deem relevant. Write down which paper you want to quote, write down who you want to mention, etc. Don't turn it into a full text yet, only put short headwords. Then, take your list and ask around at your university. A good starting point would be your (potential) advisor, as he should know both the regulations at the university and the field you are working on. If you don't have one yet, everyone with experience in this two points (other professors, PhD students, etc.) will do - you might even use this to look around for an advisor in this case.

As professors are often busy, your best chance should be to write a short mail describing your problem and asking for an appointment to discuss the list in person. Thus, your email won't land in a "to long, handle later" folder, you will already establish a personal contact, etc.