Because of how Fuji TV does shows, the only time it could return in the first half of the year is April 7th. If we make it to V-Jump and there is still no announcement I think April is off the table. After that the only other dates the show could come back this year are July 7th and October 6th, and then the first two options in 2020 are January 5th and April 5th. I find it hard to believe it'd come back any later than April 2020, but if they really wanted to they could go with July 2020 to coincide with the 5th anniversary of Super, but honestly they could still advertise it as 5th anniversary with a January or April start anyways, like Super having an "Anime 30th Anniversary" addition to the logo in January 2016 despite the anniversary not being until the very end of February.
If we are looking at a July or October return I guess the next two dates we could potentially get an announcement are April 26th, DBZ's 30th anniversary, and May 9th, Goku Day.
TL;DR
April 2019 is possible, but July 2019, October 2019, Janary 2020 and April 2020 are all probably more likely. Maybe. Who knows.