I would focus first on iPhone Duo orders, then Apple Intelligence adoption and services growth.

Pre-orders are the clearest near-term test of whether Apple can turn the foldable format into a genuine upgrade cycle rather than just a premium niche. Strong demand without excessive promotions would also support higher ASPs and margins.

Apple Intelligence matters more over the medium term. The key question is whether AI gives existing users a compelling reason to upgrade more frequently, rather than simply adding features to devices they would have bought anyway.

Services remains the most dependable long-term earnings engine, but it is less useful for judging whether the Duo itself is succeeding.

My order: Duo demand → AI-driven upgrades → services growth. If all three strengthen together, the investment case becomes considerably more convincing.