Yeah I suspected that people who used to drive to Lalor to catch the train from North Epping-Wollert/South Morang/Mernda (Doreen?) would now just go to South Morang.
The report on Monday was that the car park was half full by 6:30am and full by 8:00am, but that is normal for any train station car park - if you're not there by 7:30am-7:45am at the latest then you're usually parking in a nearby street at any train station.
At 450 spots the South Morang station carpark would be one of the bigger ones on the entire train network already (although having Glenroy's 700 spaces would be nice), so I can't see them expanding it any time soon unless it suddenly starts filling up by 7am.