Does the TLS version upgrade to 1.2 also effect CloudFront distributions

No, it doesn't apply to CloudFront distributions. The announcement you've linked to is all about AWS API endpoints. So if you were calling EC2, SQS or even CloudFront to perform some action to modify/launch/configure something in those services then TLS 1.2 is becoming the default.

For CloudFront distributions, you get to control the ciphers for your distributions. We encourage the use of newer, more secure protocols but also appreciate that there might be some clients for your applications that don't support them.