My guess is Apple will sue again if both Apple-Samsung I and Apple-Samsung II don't result in an injunction against Samsung, and if the legal decisions don't make it nearly impossible to get one. (Apple-Samsung I is on appeal at the US Court of Appeals for the Federal Circuit.) It would probably take an injunction to get Samsung to agree to any settlement acceptable to Apple.
If there is another lawsuit, Apple would choose its infringed claims/patents that it thought had the best chance of winning an injunction against the set of Samsung products currently being sold, and not necessarily those that were previously dropped. Some of the claims/patents from I/II may have expired by then, or are no longer infringed in newer Samsung products. Since Apple wants an injunction and not money, it may not be worth suing over older products.
That was exactly Apple's intent with Apple/Samsung II. Technology changes way too fast and the courts move much too slowly for timely lawsuits that would seriously impact current products. Personally I think the best Apple can hope for is monetary damages. Effective injunctions are gonna be tough unless the litigation is in Germany and even there they seem to fail over patent validity more often than not.