Apple needs, or, more accurately, takes advantage of, Samsung, the Android ecosystem, and, to a lesser extent Microsoft/Nokia and the Windows model, to reflect Apple's constantly changing state in a coevolutionary dance where Apple's adversaries are forced to test the waters of new forms that might be viable but are not yet profitable. This is currently represented in the many different screen sizes offered by the competition but has played out at other times, both large and small.
Apple allowed others to jump aboard the 4G buildout, jumping aboard itself only when 4G stabilized around the LTE standard. Others spent evolutionary cycles in efforts akin to purchasing pre-construction from an insolvent builder. Once the world coalesced around a stable set of standards with critical mass that ensured uptake and lowered costs for all players, Apple added 4G support in their products.
Apple allowed others to experiment with smaller tablet form factors, while criticizing the whole notion. Once the competition proved the viability of a market, Apple took action, entering with a strong offering that supported Apple's existing app ecosystem, provided a larger display than the competing small tablets, and maintained the full-size iPad's more practical aspect ratio.
Apple allowed others to experiment with larger smartphone displays. The introduction of the iPhone 5 borrowed from what Apple learned and changed the aspect ratio to the 16:9 aspect ratio utilized in HD video and shown as successful in many of the existing large screen smartphones. This also allowed Apple to increase the size of the display in a nod to the greater utility of a larger display, while maintaining the width of the handset that allows effective single-handed use and trumpeting this over the competition. Apple has a habit of downplaying the competition’s advantages before co-opting them.
In zero-sum games you always try to hide your strategy. But in nonzero-sum games you might want to announce your strategy in public so the other players need to adapt to it.
Is Apple playing a zero-sum game against Samsung? Not quite. Apple selectively allows other players in on its plans, and it clearly cannot hide what it's been doing once it introduces a new iPhone or iPad. Apple lets the competition know certain information ahead of time. For example, who doesn't know that a new iPhone will be introduced in September? By being consistent in its iPhone release schedule, Apple influences Samsung. Samsung knows its semiconductor/displays/memory sales will get a surge in revenues coincident with Apple's release, and it knows to set its own annual release far enough offset in the calendar with Apple's to allow itself time to mimic any new capabilities it wants from each new iPhone introduction. Apple takes advantage by keeping Samsung hooked on iPhone component revenues, just enough and only until Apple no longer needs Sammy in this respect, and also takes advantage by picking the better date on the calendar for its iPhone and iPad refreshes. Coevolution among these two competitors allows Apple to both choose the music and lead the dance.