I was planning to make this a post but didn't since it might become controversial. This is my own opinion and I hope the devs read this.
Rather than focusing on the rewards, I wish splinterlands would also do a change in its core gameplay. Yes, deck building and auto battler is good but there's honestly a very few good combinations per elements. I know there would be a change like Wild and Modern format but this feels more like a hidden limitation above the limitation when you get to bronze 2 and above, example. Before if you get to bronze 2, you may get battles that you can only use fire and water elements. With modern, not only you're limited with fire and water but also limited to Chaos Legion cards. This really doesn't improve the gameplay.
Using the same team comp every time is boring since it's just repetitive. It's pure grinding without the fun part.
By changing the core gameplay, what I mean is the rules. Rather than adding limitations like wild format, why increase freedom like adding a Unrestricted format meaning you can use ANY cards from ANY elements. Of course this would be a rotating gameplay like in League of legends Maybe it's open only every other month or every 2 months, etc.
Even yugioh changes their core gameplay to be exciting. Initially, you can summon any levels at any time, then rule change comes and you now need to tribute cards, hence tribute effects are added, then you can fuse cards, hence fusion cards added, then you don't need fusion cards to combine, synchro was added by combining woth tuner cards. Then, they thought ANY monsters can now be combined, hence link summoning was proposed, etc.
Changing the core gameplay can make the game more fun. More fun means more people would join. More people means more income and rewards for everyone.
TLDR I think a change in the core gameplay must be done first before the rewards as these rewards will change in the future and you need to change it again and then there's no change besides the rewards. Add more gamemodes or change some rules rather than implementing limitations. Hoping for the best with Splinterlands.