In today’s Apple event, the company will likely announce a new 4K Apple TV, as well as some 4K content on the iTunes Store. I wonder if Apple will provide upgrades to movies from HD to 4K, similar to how they upgraded from older 128 kbps audio files with DRM to the iTunes Plus format (256 kbps sans DRM). This would provide powerful motivation for people with existing movie collections to purchase the 4K Apple TV, after which they’d be more inclined to pay the price for higher quality movies.
This said, Apple did not do this when they moved from SD to HD movies, some years ago. So while history suggests that they may not offer these upgrades, it would make sense from a marketing point of view. More later today.
Update: Apple is offering free upgrades to 4K versions of purchased movies.