I didn't know Penske sold Aplinas.
http://www.penskeautomotive.com/
Being they are a manufacturer, and
Alpina also recently beginning to sell cars here, it's a possibility for them to join. Leaves BMW out. Would be similar to how Alpina joined GT3 before factory BMWs.
I also wonder if Alfa Romeo have talked to Penske during last season. They showed interest at Homebush and early 2017, mentioning the
Giulia and sprint Coupe could work in VASC. A DJRTP/Alfa/Shell partnership would be fantastic. Volvo came in(and switched up names/operations), were successful(also sold S60s) and left, after joining with the right team. Hope there is word on who has been talking with Penske. Waiting for news is killing me before the season starts.