...if they could add master function in the 430ex II replacement, I am definitely in.
Unlikely. There's no technical reason the 430EX II can't be a master, the control signals for Canon's optical triggering come from the main flash tube, and the 430EX II obviously has one of those. So expect a replacement 4x0EX flash to be slave only, but able to be triggered by both RF (600EX-RT or ST-E3-RT) or optical masters.
A few years ago I'd have agreed completely with this prediction however today I am not completely sure -- Canon seem to be trying to catch up by adding wireless and master capability to their smaller flashes.
430EX is a special case (from the market perspective) that is not very likely to get Master but seeing where things are going I wouldn't be surprised if Canon did just that.
Personally, I only care because I need something that can trigger remote flashes (optical or RT), doesn't necessarily have to flash itself but it needs to have solid AF assist. Even if Canon add RT master capability to their next gen cams (and I hope they will, there's nothing preventing them from doing so, especially that the business case is already there with 7D being able to be Master), I will still miss the latter -- thus I am very interested in a flash that is lighter than 580EX/ 600EX, like the 430EX replacement or (better) 270EX / 320EX / 380EX replacement -- with RT/ optical master and real AF assist (the red lights); I could use the LED light as well, but that's a minor thing.