Hi ! I would like to know if force.com domain for community is changed to site.com during winter '22

Here is the info on it. Looks like the answer is no.

https://help.salesforce.com/s/articleView?id=000358662&type=1

Potential Impact of My Domain Enforcement in Winter ’22

If a My Domain isn’t deployed in your Salesforce org before the Winter ’22 release, Salesforce sets one for you based on your org’s ID. If you prefer to use a different My Domain name, you can change it.  

When you get a My Domain, your old URLs continue to work, and users can also use your My Domain URLs. When a user logs into Salesforce, their session uses your My Domain URL formats. For example, if users directed to https://na17.lightning.force.com/lightning/page/home upon login before My Domain are redirected to https://MyDomainName.lightning.force.com/lightning/page/home after a My Domain is deployed. Your old instanced Salesforce URLs continue to work unless you change your My Domain Policies to prevent it.   

When you get a My Domain, these domains change:

• Service Cloud Real Time URLs ending in .scrt.sfdc.sh change to the format MyDomainName.my.salesforce-scrt.com.
• If the My Domain option, Stabilize Visualforce, Experience Builder, Site.com Studio, and content file URLs, is enabled, then Experience Builder for Digital Experiences URLs change. When this option is enabled, Experience Builder URLs end in *.salesforce-communities.com. If you don’t deploy a My Domain before the Winter ’22 release, this option is enabled when Salesforce deploys a My Domain for you.