Imminent means, in my and several other opinions, that they are delaying the announcement for political reasons. Everyone that I spoke with, from the SBR team to the Mayor agreed that it is "imminent", however the actual official announcement and groundbreaking date has not been disclosed. I am sure that it will be prior to the July elections. The current party will certainly want to get some traction from the announcement and start of construction headlines.
The Mexican cruisers are a big part of the decision to move forward with this project, but they are only one part of the formula. Of course, they are looking for Americans from Arizona and California. They also made sure that the new airport was adequate to handle the potential influx from all areas, both National and International, outside of the driving demographic.
No, they are not going to blow up competition hill. They have already secured a source for all the rock needed from black mountain area.