Similar photo from 2 days ago!
Before they build the new expansion, people will be using the existing parking access structure on the left of the image above, which is meant to be temporary. There is already sliding doors installed on the departures level, which currently goes to a blank wall, and will connect you to the existing pedestrian bridge. Here you can see they’re the same level as the elevators:
But this could be changed and a new temporary bridge could be made, the current one has very bad ventilation/airflow so it wouldn’t be the best experience for someone to take the REM.
So you will have to go outside, but only to cross a single street, and this will be temporary until they move the drop off zones on the other side of the station (approximately where the first photo was taken from)