Hard to say. 75k for sure, but probably around 125k would be my estimation across all languages and variations.
I make lists of all languages and variations of a single Pokémon pretty often. For now, I’m just gonna ignore generation 8 completely, as well as the lists with the most and least amount of individual TCG cards across all languages and variations (i.e. Pikachu (>1250); Unown (~1000); Charizard (~660); Raichu (~600); …; Mantyke (17); Bonsly (17); Chingling (~25); Mine Jr. (~30)). The average I’ve seen of the 87 lists I’ve made thus far is around 125 or so (actually higher due to the many generation 1 Pokémon lists I’ve made, so I’ve lowered it a bit). Multiply that by the amount of Pokémon in the first 7 generations (809), I end up at 101,125. This is without any generation 8 Pokémon, but those can be ignored in this rough average. BUT, it’s also without any Trainer nor Energy card in any language, which would definitely add at least 20k more cards.
Also, I think this amount will probably continue to rise pretty rapidly in the years to come. In 2019 alone more than 200 Pikachu cards have been released across all languages and variations. This is mostly because right now there are 11 languages actively releasing cards: English, Japanese, German, French, Italian, Spanish, Portuguese, Korean, Chinese, Thai, and Indonesian. Based on what we’ve seen with Dutch, Russian, and Polish cards, as well as Chinese in the past, I don’t think Chinese, Thai, and Indonesian cards will continue for years and years, but the other eight languages are pretty consistent (Spanish, Portuguese, and Korean maybe not very consistent for every set, but they do still print cards almost every year). And who knows, maybe even more new languages might be added in the future.
Greetz,
Quuador