Tether Holdings Ltd. expects close to $15 billion in profit this year, as the stablecoin issuer’s rapid growth continues to attract investors keen to back the closely-held company.The El Salvador-based firm, which issues the world’s largest stablecoin USDT, grabbed the attention of financial markets last month after Bloomberg News reported it’s in talks to raise up to $20 billion in exchange for a roughly 3% stake in the business. Such a deal would value Tether at around $500 billion, propelling...