The latest with the Miami Intermodal Center is that the 28th Street bypass work was completed on August 12 but it doesn't look like Amtrak will move there anytime soon. My guess is that the carrier may be disinterested in relocating because it doesn't want to do 14 miles of backup moves each day.
It is worth noting that the MIC was built primarily with high speed rail in mind. Given that the Florida HSR has been dormant for almost six years, it is unlikely that the project is coming back--even with a pro-HSR governor in 2019. Another factor is that the previous Amtrak leadership and FDOT officials clashed over platforms, it's unlikely that a new Amtrak administration is going to be any more receptive to leaving the current station in Hialeah, nor that it's going to revive talks with state officials.
So, the end result is that Miami will end up with three separate train stations: Hialeah for long distance trains, an oversized airport location for Tri-Rail, and a grand downtown station for express intercity trains and select Tri-Rail trains.
The only possible thing to alleviate the MIC's potential under-utilization is for the FDOT to step up and implement corridor service in the vein of Sunrail and California Corridor and having such trains using the Airport Station.
Of course, to get to an intra-Florida passenger rail system, the current government has to either be voted out or step down in less than two years' time because as it turns out, Amtrak was the one to reach out to Florida on providing in state service but the state said no thanks.