I tried to search if the OP_RETURN was no longer accepted by the network, but in fact it is. But I have read that it first allowed 80 bytes of information, and then they lowered it to 40 bytes... Who knows what they might do to my new best friend OP_RETURN in the future...
No, it was 80 bytes (I think never deployed though), then lowered to 40 bytes, then now it is back to 80 bytes.
The 0.12 version will allow multiple push in the OP_RETURN, but the limit will still be 80 bytes for all data (more precisely 83 bytes for the OP_RETURN script)
OP_RETURN is relatively safe, I don't think devs will break anything here since it does not cost anything on the UTXO set and is prunable.
If you want a reason not to use OP_RETURN, it would be if the fee rate rise so much than the added value of using OP_RETURN for your case is not worth the price of the added bytes in your transaction.