Hi Kevin,
To troubleshoot the issue, I'd like to double confirm the situation and collect the following information:
1. Do you mean that the Office 365 upgrade has lasted 14 days?
2. From the description, I see "We are holding off on an upgrade to Exchange 2013 on premises ..", I'd like to confirm whether you've deployed Hybrid on premises.
3. I see "my portal still says it is being upgraded.", could you capture a screenshot of the issue and post here for further research?
Thanks,
Aaron Yuan