I have been thinking for a while to include a script that will let you upgrade to the latest and greatest OctoPrint, and would also include rollback support.
I have a feeling other people have already things they use, so please feel free to share your snippets so we can get the best result.

Meanwhile you can update manually using:

cd ~/OctoPrint ; git pull origin ; ~/oprint/bin/pip install -r ~/OctoPrint/requirements.txt