Depends on what you mean by "contender" but Rashid Yusupov would be a great pickup imo, even if he wouldn't be near the title for a while. He's hit a rough patch but he's still only 28 and is 1 - 1 with Viktor Nemkov, his best years are still ahead of him. With his very technical fading and countering style I feel like he does much better when he can prepare for a specific opponent (outside the PFL tournament format). He had a ton of trouble countering and stopping the wrestling of Viktor their last fight, whereas he seemed consistently a step ahead the first time. I guess you could include Jordan Johnson, but he's already 32 and has plateaued as a mid-tier blanket, I just don't think he's going to develop much more, I don't see him being a contender in the future. Stephan Puetz is on a nice can-crushing run right now, he might be worth filling out the middle tier of a division with.
But yeah, other than Sordi who's locked down in the PFL, and Narkun locked in KSW, pretty much all the bright prospects from mid-high tier orgs have been split between the UFC and Bellator. As a lot of people have commented, I think Bellator was actually a step ahead with notable free agent LHW signings the last few years; UFC picked up Jiri and Khadis Ibragimov (he REALLY sucks now unfortunately), whereas Bellator got both Nemkov Brothers, Yagshimuradov, Albrektsson, Biyong.