70 new Pokemon does make sense whatsoever. If you subtract the amount of Pokemon as of now (719, this generation's Mew is 719) with 1000, you would get 281 Pokemon left remaining. If I were to say Generation VII were to receive 130 Pokemon, that would make 151 Pokemon left for Generation VIII. We're only a couple of years away from the 20th anniversary, so perhaps they're trying to limit the amount of Pokemon and surprise us the 1000th (or 1001th Pokemon) for the 20th anniversary? Perhaps a return to Hoenn a year and a half from now with Z being released in the same year (FRLG and Emerald were released under one year together, just months apart)? Who knows, maybe there could be more than 70, we just don't know.