Bar Nosh: If you’re true concern about “too many Sephardic families are sending their Bochrim to Ashekenazic Yeshivas” was beacause they are losing their “culture”, then why would you bemoan that “very, very few Ashkenazim send their Bochrim Sephardic Yeshivas”? You should be please about the latter, since in your view they would not be losing their Ashkenazic culture.
Torah is Torah, whether in an Ashkenaz Yeshiva or Sephardic. There has been cross-over Yeshiva attendance throughout the ages.