I will be very surprised if this year's a-nation 2019 will have no Tokyo dates
But a-nation hasn't finalised the details yet , even the general ticket balloting for the 17th & 18th Aug dates in Osaka have not been released either unlike for Aomori , Mie & Fukuoka
Assuming that this year's a-nation 2019 will once again be held at Tokyo's Ajinomoto Stadium , 24th & 25th Aug looks more likely it will take place
https://www.ajinomotostadium.com/schedule/2019/08/
Nothing listed for 24th & 25th Aug , so far