Should I buy now or wait for the next model?

Handhelds refresh constantly, so "wait for the next one" is always technically true and rarely the right call. The honest framing is price-per-performance against the ceiling you want: if a current device clears your target with headroom, buying now gets you playing and the next model will not change your ceiling. Wait when a device sits right at the edge of your target and a known imminent release clears it comfortably, or when a current model is late in its cycle and a refresh is clearly close. Otherwise, the best handheld is the one you are using.