I beat the drum pretty regularly on infinite progression potential, since everyone needs motivation to keep striving, no matter how much they have already achieved. Hard scaling to make end-game progression is important to ensure competitiveness, but the critical goal is to make sure there’s always something exciting left to do. Here are two ideas that could help out with that:
The Keeper of Souls offers you a bargain, though as with any of his offers, the price is heavy. You must have ALL troops that you own fully leveled, and one million additional souls as well. Accept the Keeper’s bargain, and you lose one million souls, plus all of your troops lose their levels back to 1 (you keep traits, guild & kingdom bonuses, etc.) - but all of your troops gain +1 permanently to all skills. Your name also becomes green in global chat to show off your achievement.
You can do this a total of four times (green, blue, purple, orange - teal is for devs and mythics only), and the price increases each time. 2M souls for the next +1, then 3M, then 4M for the last. Not a permanent solution, of course, but 10M souls is still a ways away for any players.
Every time you pull a card, there is a tiny (1 in 10,000, or even less?) chance that it is a “foil” version of that card, which confers a special bonus. A foil card gains a similar +25% like event week troops and a special chevron indicating the bonus, but the bonus is permanent for that troop. If you are fantastically lucky, you can stack a second foil bonus on the same card - meaning a potential for four bonuses during the card’s event week.
The odds of getting a foil are low, but they would mean that even end-game players would still potentially get something useful and fun even out of gold chests. Base common cards that had been long ignored might become suddenly competitive and usable.
Feedback, suggestions, improvements, and your ideas for infinite progression are welcome!