I worked for Atlas and have friends at Kalitta. Honestly, it doesn't make sense to leave one ACMI carrier for another. Yes, I truly believe Atlas will outlive Kalitta based on management team and overall business strategy, but the real question is "What are you after in life?" ...probably not a question suited for this forum.
You either chose ACMI for 1 of 3 reasons. 1. You enjoy the lifestyle of seeing/experiencing the World. 2. You are using it as a stepping stone to a 'Major.' 3. Your current qualifications/background/experience/perspective limit you to this Company.
The majority of ACMI pilots only leave their Company due to Bankruptcy. History has proven that. If you feels Kalitta is going under soon, then JUMP!