The reason I disagree with what you are saying about old cards going down in value long term is that so little of land has been released right now. Look at how much impact the grain LP has had in such a short time. Look at the staked DEC on land, it's constantly going up now. We are already at $35k liquidity in the grain LP and it's only been about a week. Next is going to be the research leaderboards titles which means people will be fighting over those rolling titles which will require grain.

I just don't understand how you read the white papers for land and don't get it, how this will not make old cards valuable.

Every tiny thing they release for land is going to act like a leverage of stimulus to the economy as long as they make it somewhat relevant to ranked.

Example A

Lets say next month or the month after that, they release the salt system. Players that own at least 2 surveyed land plots will now earn SB desalinization crystals in ranked. Now we can start desalinating our land to reduce our trading fees, our taxes and boost our production. On top of that, on the other end, we will earn salt tokens. Salt tokens in the white paper can be combined with potions to create something called "enhanced potions" but what if they let players use their salt tokens in the 2 week run up to a promo event. "The company is letting you use our alchemy lab temporarily during this promo event to create enhanced potions" and you can apply those to the promo cards and also to jackpot chests.
Now all the old players with thousands of potions will start making these enhanced potions that can be sold on the market.

Example B

None of the magic plots have been released/enabled yet. What if they release/enable the next 2 magic plots and they match the same elements of the next legendary summoner airdrop?
And they make it a requirement that you produce and burn on the wagon a specific number of those same magic resources in order to qualify to get the special skin of that summoner. How much do you think that special skin is going to be worth? And this will drive up the price of grain.

I think the problem with the land white papers is too many people went to sleep trying to read it because of all the details. All they have to do is start releasing/implementing little parts of it and make it relevant to ranked.