You may be offered this free upgrade or indeed been offered it already. My advice at present is to hold back for a few months as there are a few error messages that can appear after the installation.
The error message reported does not affect your machine in anyway and 8.1 will work without any issues, but the error message will continue to stay for a time period that I cannot yet answer as it is unique to each machine.
The great thing is that you are not missing out by not having 8.1.
This is my advice only but please make your own judgments on the upgrade.
Regards
Neil
