Upgrading Python 3.6 to 3.7 in Ubuntu 18.04 LTS

No

Ubuntu uses a snapshot method of populating the software repositories. After release, the only changes are for security and major bugfixes. In addition, a great deal of the system depends upon a specific version of python - upgrading python may break those services (like apt).

Historically, Ubuntu has never upgraded to the next major version of Python or Python3 during a release. All upgrades occur during pre-release testing.

If you need the newest python version, I recommend to use python environments like Anaconda or others. The Pros are that you can install several environments with different python and package versisons with a tool called conda. So you don't get problems with your system python's.