I have a theory about what they are doing and why they are doing this. Is it possible that the devs are ironing out the bots in Modern format so that once Modern Format is 100% non-bot, they can now let the cards be released?
By that, I mean, they would make Modern format in a way like in wild format that you can use all cards ONCE they solve of the bot problems in modern?
Imagine it as playing League of Legends and has both Solo Queue and Flex Queue. Both format, you can play any champions you own and yet, they are different queus. You can still play solo while doing the Flex queue and it won't affect your solo queue standing.
So, in Splinterlands, maybe once they fix that there are no bots in Modern, they can now release the restriction and you can now use ALL of the cards in that ranked format.
Just a theory.
It would be very good news... but since they don't seem interested at all in a full bot ban, don't see it happen on the near future. Would love to be proven wrong.