You don’t have to build with armv7s right away.
And despite user demands, you also don’t have to support 16:9 right away either.
It’s fine to get real hardware into your hands. More than fine; it’s being responsible. Apple has you covered with letter boxing; let the 16:9 screen be their problem until you’re really ready to take full responsibility. By all means, do whatever development and simulator testing you want now. But wait for real hardware to ship.
Always measure before cutting.
(But measure and cut quickly.)