I'm not bashing any of these. Love my 452s because they have proven their worth to me. The 455 barrel swap is a great option for individuals who live in restricted areas and might be limited to the number of guns they can own. A 455 expands their options for calibers. It also offers custom aftermarket barrel options for the accuracy chaser. The 457 will make a lot of guys in the USA happy because they finally have their "correct" safety.
I have no idea what CZUB or CZ-USA are planning but if it were me I would setup 2 product lines. Keep the 455 and then promote the 457 as an upgraded version with the upgraded bottom metal, torx screws, adjustable trigger, lighter weight, etc. I would hate for them to lose their "affordable" quality niche they have.
One thing I love about all the changes; the mags never changed and are interchangeable. Maybe someday I'll find a deal on a 455 and add one to the mix. Just found a 452 Varmint that I couldn't turn down cause it came with FOUR mags.