This is likely bad news for most altcoins like Ethereum, solane ,Tron, BNB, and others, since people mainly use them for tokenized dollars
I dont think its really bad news honestly for Ethereum, might be bad news for others though.
The reason people use something like tron is to avoid high fee on ethereum, however now that these stablecoin issuer are creating their own token, no more tron use anymore and so on.
ETH on the other hand have one big reason why people still uses stablecoin in there which is to find yield from onchain defi.
Even if USDT and USDC establish their own blockchain, ETH won't lose its TVL.