Will the new nexus,inhibitors and minions be on the other maps?

Nothing is for certain. They've said they aren't sure what this update will mean for the other maps. Most likely it will depend on how PBE testing goes and how well the visual update is received by the community when it goes live. They also have the concern of making sure that they don't overextend the scope of this visual update to include other maps until they get a solid return on their resource investment.