JetStar Pacific (VN) took in high timer F/Os for its 1st leased A320 last July with the promise of command upgrade when the 2nd acft arrives, projected then on Nov 2008. They ended up being loaned to Tiger in SIN instead.
Moral of the story is obvious: The company can make all sorts of promises, written or otherwise, but the fine print (there is always one) still allows them room to extricate.