I've wondering why Airbus has never, and so far isn't planning on, competing with the Boeing 757 series of airliner. The A321 is somewhat a competitor for lower-mid range 752 ops but for instance can't fill the 752's longer range pond-crossing market
Let's look at the 757's history first. It development was two fold, first as a 727 add-on and then later morphed to parallel the 767. Boeing developed the 767 as a replacement for the 707 and as a competitive move against the new Airbus twin-jets. The 757/767 were designed to offer airlines a quasi-common family of aircraft offering both narrow and widebody economics to fly hub-spoke routes, regional widebody routes, and then later, long-range ETOPS routes.
So in a sense, the A300/A310 were the inital counterparts to the 757/767. Naturally when the A321 came along, the 757 was the closer counterpart, but the A321 is a stretched A320 designed primarily for charter opperators. Hence, the A321 doesn't have the uplift or range of the 757, they were designed for completly different missions.
While Boeing has closed the 757 line it is releasing the 7E7-3 which will cover most of these market segments. The A321 has never been a real 757 competitor and will be even less a 7E3 competitor
The 7E7-3 is another regional widebody in the tradition of the A300/A310 and 762A/763A. It's the short-range counterpart to the 7E7-8, just as the 757 was the short-range counterpart to the 767. The 7E7-3 is being billed as a 757 replacement because it has very low seat/mile cost, but in reality, it is far to big to replace 757s directly.
The A321 and 7E7-3 are obviously in different worlds.
The new A350 that's in the works won't be a 7E3 competitor either. Why has Airbus ignored the important 757 market?
The A350 is rumored to have a counterpart called the A30X... something of a 7E7-3 competitor.
Airbus has had quite a bit of success targeting Boeing's markets, why not this one?
Airbus hasn't targeted this niche because it's mostly gone, nothing or noone to sell to. The 757 will probably be replaced by a mix of 737/A320 and 7E7-3, but no direct sucessor....
In the 1980s when the 757 was at its prime, Airbus was heavily invested in the A320 and A330/A340 development. Later in the 1990s, the 757 began to wind-down as most demand had been met. The A321 was also available, and got some market share. At the end of the 90s, the demand for the 757 was almost non-existant. Boeing tried very hard to win additional orders, but was empty. They announced the closing of the line, and no customers made much of a protest