Proposal for macOS Intel Support deprecation timeline in ITK 6 (Retained in ITK 5)

### **Proposal**

Deprecate macOS Intel (x86_64) support in ITK 6, while maintaining it in ITK 5 as a long-term support (LTS) release. This aligns with Apple’s phased sunsetting of Intel Macs and industry-wide shifts toward Apple Silicon optimization.

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### **Rationale**

**1. Apple’s Official Transition Timeline**

- Apple completed its transition to Apple Silicon in June 2023 with the Intel Mac Pro’s discontinuation[^4].
- macOS 17 (2026) is projected to be Apple Silicon–only, ending major OS updates for Intel Macs[^2][^3].
- Security updates for Intel Macs will continue until ~2027 for newer models (e.g., 2019 iMac, Mac Pro) but lack feature parity[^2][^5].

**2. Third-Party Software Trends**

- Major developers (e.g., Adobe, Microsoft) now prioritize Apple Silicon optimizations, with some dropping Intel support entirely[^2][^5].
- ARM64 macOS now dominates developer toolchains, with Xcode and CI/CD pipelines increasingly excluding Intel[^5].

**3. ITK Maintenance Burden**

- Supporting legacy Intel macOS complicates builds, testing, and CI/CD for ARM64-specific optimizations.
- macOS Intel GitHub Action Runners (`macos-13`) are slower than the ARM counterparts.
- Deprecating Intel in ITK 6 allows focused resources on Apple Silicon performance.

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### **Proposed Implementation**

- **ITK 6**:
- Remove Intel macOS from build matrices.
- Document deprecation in release notes, directing users to ITK 5 for legacy workflows.
- **ITK 5**:
- Maintain Intel macOS support as an LTS branch until 2027 (aligned with Apple’s security update window).
- Backport critical fixes only.

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### **Community Impact Considerations**

- **Affected Users**: Researchers/clinicians relying on older Intel Macs for specialized hardware (e.g., GPUs, PCIe devices).
- **Mitigation**: Provide migration guides for Apple Silicon or Linux/Windows alternatives.
- **Timeline**: Target deprecation for ITK 6.0 (Q1 2026), coinciding with macOS 17’s expected release[^3].

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### **Supporting Data**

| Key Fact | Source |
| :-- | :-- |
| macOS 17 (2026) likely Apple Silicon–only | [^2][^3] |
| Final Intel Mac (Mac Pro) discontinued June 2023 | [^4] |
| Security updates until ~2027 for newer Intel Macs | [^2][^5] |
| Average 2-year security update window post-OS EOL | [^2][^3][^5] |

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### **Request for Feedback**

Please share:

1. Use cases requiring Intel macOS support beyond 2026.
2. Concerns about legacy hardware/software dependencies.
3. Preferences for LTS backport policies in ITK 5.

*References inline via linked sources. Data current as of April 2025.*

[^1]: https://www.reddit.com/r/MacOS/comments/18dt837/how_much_longer_for_intel_macs_lets_hear/

[^2]: https://9to5mac.com/2024/06/19/got-an-intel-mac-future/

[^3]: https://9to5mac.com/apple-intel-mac-support/

[^4]: https://en.wikipedia.org/wiki/Mac_transition_to_Apple_silicon

[^5]: https://computercity.com/desktops/mac/how-long-will-intel-macs-be-supported

[^6]: https://discussions.apple.com/thread/255950497

[^7]: https://forums.macrumors.com/threads/rules-for-mac-os-dropping-hardware-support-and-for-retiring-mac-oss.2415471/

[^8]: https://www.pcmag.com/news/how-long-can-you-keep-using-an-intel-mac

[^9]: https://discussions.apple.com/thread/254657045

[^10]: https://www.refurb.me/blog/are-intel-macs-obsolete

[^11]: https://eclecticlight.co/2024/08/06/how-long-does-apple-support-mac-firmware/

[^12]: https://news.ycombinator.com/item?id=41176265

[^13]: https://en.wikipedia.org/wiki/MacOS_version_history

[^14]: https://en.wikipedia.org/wiki/Apple_silicon

[^15]: https://www.reddit.com/r/mac/comments/1g93ctg/macos_16_is_going_to_drop_support_for_all_intel/

[^16]: https://discussions.apple.com/thread/8415153

[^17]: https://endoflife.date/macos

[^18]: https://9to5mac.com/2022/12/15/apple-silicon-transition-timeline-mac-pro/

[^19]: https://support.apple.com/en-us/100100

[^20]: https://forums.macrumors.com/threads/will-macos-15-drop-support-for-intel.2421008/