I highly doubt Toonami would be dumb enough to wait on Super. They'll likely air Kai and Super side by side like they did with Naruto and Shippuden for awhile. Juding by how long it took for Kai to air on US TV my guess is thar Super will start airing on Toonami around August or so.
I'll hope that will be the case, but they really don't have any reason at all to rush airing super. The market will be there regardless how long it takes.
I mean it really wouldn't be dumb on their part at all.
if you look here you can see a ton of
toonami numbers
DBZ kai kicks off their anime block on saturday
on august 8th dbz kai set the all time high viewer numbers for toonami's reboot
those numbers are quite a bit more healthy than when it first started airing.
if we look back when it first started airing we can see that dbz kai instantly takes over the top ratings for the block despite not being the first aired show.
from there attack on titan takes back over the top spot by a very small margine for the next few weeks and dbz kai stays really strong for them for the whole time despite being aired on cartoon network years after its original release and these episodes already having been released on nick or disney hd I can't remember which.
source (finding the actual data takes a while :/
nov 15th if you want it)
tl;dr: dragon ball gets toonami numbers with new episodes. I am not showing the numbers there but the reruns attract half the people a few hours before the new episodes. They will want to keep that strong lead in as long as possible.