If they would keep what they told when releasing Untamed all would be fine:

https://steemit.com/splinterlands/@steemmonsters/splinterlands-untamed-info-and-release-date

Unfornately Splinterlands has left this goal behind startung with submitting the legandary Untamed Summoner so that now nobody needs Alpha/Beta-Cards or only very few cards you can use in rare cases.
If you now take also away tournaments for Alpha (& BETA)- Cards means that you devalue the old cards completely.

The problem is (and this you see when you look how the general-sale run) that in this way you have very big problems to sell new sets as investors will always think that what happened with Alpha & BETA-Cards will in some yeare happen with Rebellion-cards latest at the point they will move out to wild (but clearly the price-drop will start much earlier), so what investor want buy expensive cards who he can sell only for a cheap price in some years.
Like at the stoke exchange - Nobody will buy a share for 100$ when he expect that in 3 years this share will have a worth from 10$.