Sure, it's not impossible. But PC cruises have been rare lately, this will be the first one on the Magic (I think?), and platinum folks seem to always take the concierge rooms on the unique cruises.We booked our EBPC in 2016 when we were silver. That was our first concierge cruise, too. It can be done. The demand is usually pretty low (for Disney) for the PC cruises due to them sailing when schools are typically in session.
Still, you never know! It might work out for your this time. And if you don't want to sail concierge (starting at $17k!), then you probably don't have much to worry about. You'll get a room.