It's quite simple really. Never, and I mean never, leave a good job to go to one that is making a promise of Captain/PIC in some period of time. It rarely ever pans out that the promise is kept. Only airlines with established seniority systems can ensure an upgrade, but even then they can't make a promise as to the timeframe. These contract jobs are especially bad at keeping promises. Just look at all the guys who have bailed from Eva, China Airlines, Qatar, etc over the years. At least Vietnam and Korean are up front about expat F.O.s never getting an upgrade.
Typhoonpilot