Yeah, I've harped on this before so, apologies if I sound like a broken record. But it's not about assuming everyone comes back. It's about doing the things within your power as a coaching staff to bring as many back as you can (so long as you actually want them back) because continuity is like compound interest on an investment.
Coaches have a ton of influence over whether a player transfers or not. So, there's no reason to think they won't use that influence to try to get guys to run back what is shaping up to be a special year.