As of now, we haven't received any guidelines on how RoboCup Junior will run an organise the competition for 2020. I understand there are a multitudes of questions that participants and mentors would like answering, such as age restrictions and rule changes. I cannot make official comments on such questions because these are out of the TC's control, and I do not wish to spread misinformation (but I am sure that these will be answered in due course, in all fairness to participants ).
(Personally) Regards to the rules, I would be surprised to see any major changes (if any) for the competition in Bordeaux. If changes will be made, a large proportion of them would be to include clarifications and corrections made on the 2020 rules + changes to mitigate easily foreseeable organisational issues.
I understand that vague answers do not help much, but this is the extent we know as well unfortunately. We will keep updating new information.