"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Seeds Third Beta of iOS 10.3.2 to Developers and Public Beta Testers
Registered developers can download the third iOS 10.3.2 beta from the Apple Developer Center or over-the-air with the proper configuration profile installed.
Apple doesn't typically provide detailed release notes for its iOS updates, so we don't yet know what features, improvements, or bug fixes might be coming in iOS 10.3.2, aside from some fixes for SiriKit car commands, outlined in the release notes for the first beta.
As a minor 10.x.x update, we can expect iOS 10.3.2 to offer bug fixes and performance improvements rather than outward-facing features. No notable features were found in the first two betas, but if anything new is found in the third iOS 10.3.2 beta, we'll update this post.
Update: Beta 3 is also available for members of Apple's public beta testing program.