Modern Family cast members Ty Burrell, Julie Bowen, Jesse Tyler Ferguson, Eric Stonestreet and Sofia Vergara (all the primary adult cast other than Ed O'Neill) have filed suit to void their contracts according to THR. The move is the latest salvo in their contract renegotiation efforts with 20th Century Fox TV which produces the ABC hit comedy. Earlier today, a table read was cancelled at the last minute.
O'Neill is renegotiating his contract separately, but as the more established actor was reportedly already making significantly more than the others. In the wake of the show's success on ABC which has already been sold into syndication (where it will begin airing this fall), it's hard to find fault with them wanting more money. But since they're already under contract, unless the suit is successful I'd be surprised if they get exactly what they want. But it should still amount to truckloads of cash.
As you can tell by the poll below, despite escalating contentiousness I will be surprised if things are not resolved soon enough for Modern Family to debut on schedule in late September.