I think the Splinterlands Devs are on the right track. As to what track that is, I think they're seeking to be like of Riot's type of business, the main creator of League of Legends. Why do I make this comparison?
Before League, there was DOTA Defense of the Ancients map that was made for Warcraft 3. This is the start of Team MOBA games like League and DOTA 2. Warcraft's creator is Blizzard which is now on downfall while Riot, creator of League of Legends is on the rise. Riot's goal is to make multi-games surrounding around one universe/lore. Imagine MCU. Currently, they have League of Legends (MOBA), Legends of Runeterra (Card Game), two other games that I haven't played yet, Arcane (An anime), K/DA (Music video), and on the production, an MMORPG based on Arcane's Zaun city which is based on League of Legends Lore.
TLDR: Splinterlands is making its expansion on their games and probably tie it off with SPS. Meaning each game may have different coins but have one general coin, the SPS, and probably VOUCHER for limited contents. Does this kill Splinterlands? No. On the contrary, I think it improves it because people who might hear of the waka project (just calling the game that), may now search for Splinterlands and if they're card games nerd like me, they might transfer from the Waka Project to Splinterlands just like how I transferred from League of Legends to Legends of Runeterra.
A boom in the developers is a success in all their games overall is my TLDR.