The 2018 Royal Rumble show will have both a 30 man Royal Rumble as well as a 30 woman Rumble on 1/28 in Philadelphia.
The idea of doing equal matches means that a number of wrestlers from the past or women in developmental will have to be called up since there are 18 women on the active roster between Raw and Smackdown and two of the 18 won’t be in because they are the champions. It also eliminates both champions from wrestling on the show in theory, since they already did the champion vs. champion match and all the other women have to be in the Rumble.
In addition, that would also in theory mean roughly two one hour matches on the same show, unless they cut the entrance time down. Usually the entrances are at intervals whenever the company wants them, but are usually announced at two minutes, but often are closer to 90 seconds and have been 60 seconds at times. I’m not sure the women’s Rumble needs 30 participants but there will probably be surprises involved.