Then you would be travelling on your EEA RC after the end of the transition period, which is what we have been trying to avoid from the begining, since this might also be a risk, in the case the EEE RC card is not valid after 31st December 2020.
I am not claiming that all the precautions I think of are actually necessary, I tend to err on the side of caution. Again, the real problem is that no one knows for sure how it all works, what will be valid, and what not, until empirical evidence and testimony of people experiencing it first hand is available (probably during the first couple of weeks of 2021).
It's a catch 22 in any case. Hence, as I have said here three times already, the only way of being 100% sure to avoid any issues is to not travel at all until you have a new EUSS RC in your hands. Not saying this is the right thing for everyone to do, or that it is necessary, but it is, as of today, the only thing we are sure of that will prevent any problems.
