If it's a critical production server (where downtime is not an option) then don't upgrade now ..(you can do that when you are sure of 5hrs of less to no traffic on your server)
I say this because, plesk's upgrade stability is unpredictable ..(while others experience a smooth and clean upgrade, others end up with broken servers and there is no systematic formula as of the cause)
You may also want to try using Parallels Plesk Panel Pre-Upgrade Checker: A tool to identify business logic issues before upgrade or migration