The user will need to accept the new policy to continue his account. Users will not get any option for this. However, right now there is also the option of 'Not Now'. Meaning if you have not accepted the new policy for some time, then your account will continue to run. The new policy has more integration of Facebook and Instagram and now Facebook will have more data of users than before. WhatsApp's data was also being shared with Facebook in the past. The company has made it clear that the integration of WhatsApp and Instagram with Facebook will be more.
In the updated policy of WhatsApp, some things have been written in the license you are giving to the company. It states that to operate our services, you use WhatsApp to upload, submit, store, send or receive content worldwide, non-exclusive, royalty-free, to use, reproduce, distribute and display the content, Sublicensable and Transferable licenses.