The Binance Chain Mainnet will be launched on April 23rd, 2019 which will also involve the swap of the BNB tokens.
The announcement was made on the official Binance community website, although it is stressed that the date is an estimate and may be subject to change, depending on how things go.
The Binance Chain Explorer and the Web Wallet will be made available to selected partners for testing, and will then be open to public access around April 23rd, 2019. The calendar of events is the following:
On April 18th all the pre-selected validators will be online to produce blocks with consensus starting from the genesis block. The native currency, Binance Coin (BNB) will be created already in the genesis block with the BEP2 standard of Binance Chain. The total initial supply of BNB will be 200,000,000 units.
As with the current BNB ERC20 token, 11,554,398 BNBs will be burned on Binance Chain, and 48,000,000 will be frozen, so as to achieve the same total supply and circulating supply as the current token.
The first batch of the new 5,000,000 native BNB tokens will be assigned and deposited at an address belonging to Binance.com in order to convert the old ERC20 tokens for existing owners. Binance will also burn 5,000,000 BNB ERC20 to keep the total supply of BNB constant.
As users convert the old ERC20 tokens into the new native BEP2 tokens, more BEP2 coins will be released and proportional amounts of ERC20 will be burned to keep the total supply constant on both networks.
If everything works as expected, users will be able to provide their new Binance Chain address to receive the new BNB tokens, with a mechanism converting the old ERC20s into BEP2 tokens.
However, on the Binance exchange, no trading pair will be listed until the first batch conversion of BNB is performed.
If you want to keep the ERC20-based BNB tokens, you can withdraw them from your Binance.com account to an Ethereum wallet, but only before 2 AM (UTC) on April 23rd.
However, the BNB ERC20 tokens will all be migrated to Binance Chain, and after April 23rd Binance.com will no longer support the withdrawal of these old tokens.
The exchange will still support the deposit of the old ERC20 tokens in the future, but it is highly recommended to convert them to the new BEP2 tokens.