It is almost impossible for the Democratic Party to abandon Biden and the president has given no indication that he intends to step aside. In the modern era, a national party has never attempted to replace its candidate in an adversarial manner.
An anti-Biden coup at the convention is theoretically possible, although highly unlikely. If Biden were to withdraw between now and August, it would likely create a pitched battle at the Democratic National Convention in Chicago. The only plausible scenario for Democrats to get a new nominee would be if Biden decided to drop out, as Lyndon Johnson did in 1968.