I voted keep the 600, no 430 update. Unless Canon goes to RT in the body you need another flash or the STE3 to make RT worth it. If you are going off camera then you are looking at modifiers down the road that require more power. I think serious off camera shooters will want more power. YN will not come not come out with a smaller version of the 600 clone (whenever it comes out) just because it will be reasonably priced and there will be competition from others one day. Besides if Canon comes out with a 430 RT why would people buy it when they can get a YN 600 for the same price.
I think Canon will keep the 430 non RT for you basic single flash on camera photog. They may update it to make it sound more fancy. Heck they may even just drop that line one day which would make the 320 the basic intro flash. I could be wrong but YN came out with their own transmitter within 2 years of Canon's STE3 which is ½ the price. As a business you have to think about R&D and manufacturing change costs vs return on investment. I'd focus on pricing current RT products more competitively. They are going to feel it when YN comes out with the RT flash. Others like Godox are around the corner.
I don't believe so. People with >$2,000 cameras and $450 flashes are not as concerned about saving $100 on a trigger, and the YN-E3-RT is only $100 less than the ST-E3-RT. The YN-E3-RT's big/only selling point is the added functionality primarily for pre 2012 bodies, if the YN-600-RT is only $100 less than the 600-EX-RT then I don't see it being the run away success so many forum posters do, the Phottix Mitros+ is $399, a mere $46 less than a 600-EX-RT!
The choice of third party flash systems and functionality is a big and growing area, but like tripods, after all the headlines and excitement have died down the reliable and solid performers win through. Canon flashes will always work on Canon cameras, Yongnuo/Godox/Phottix flashes might work on Canon cameras if you have a copy of Windows 7, the latest firmware, and Yongnuo/Godox/Phottix are still supporting it, though their MkII versions might not and are unlikely to work with their MkI versions anyway. For most people in the >$2,000 cameras and $450 flash market that unknowable current and future compatibility and untested configuration reliability is worth way more than $50-100.