"The Avengers 3" will be coming in 2018, probably. Given that Avengers opened at the beginning of May 2012, and we're getting Avengers: Age Of Ultron at the start of May 2015, it makes sense that the 2018 release date will be when Avengers 3 is coming.

Speaking to Comic Book Resources, Feige unveiled the non-confirmation confirmation in regards to what exactly that release date for "Avengers 3" will be. 

"Well, we haven't really talked about what we'd see Avengers 3. I presume we'd like to stick to three years between Avengers movies like we did [between the first and second]. So it will probably be three years between Avengers 2 and Avengers 3."

Marvel has three release dates set up for 2018. In addition to the May 4th date, they'll be premiering a currently unnamed film on July 6th, and yet another will continue the Marvel Cinematic Universe adventure on November 2nd. Those are good release dates, but they aren't first-weekend-of-May-quality release dates.

Phase 3 is definitely starting to take shape. We know that "Ant-Man," "Captain America 3," and "Guardians Of The Galaxy 2," are on the way, and there's also a July 2016 Marvel movie that almost surely Doctor Strange. There are also three scheduled unnamed 2017 releases, one of which is most likely "Thor 3"

Although Marvel has also claimed July 6, 2018 and November 2, 2018 release dates, as Cinema Blend notes, these aren't on the same level of the first weekend of May.

"Avengers 2," of course, is set to hit theaters on May 1, 2015.

In the same interview with the CBR at Comic-Con, Feige also suggested/ then immediatley hinted the opposite that Thanos isn't in the plans for "Avengers: Age of Ultron" 

"He's not a part of Avengers 2. I think Thanos kind of does what he wants, shows up where he wants to. And I'm not going to tell him otherwise, so you don't know exactly. Smirking at the end of the first Avengers. But you know, we're still making Avengers 2, so nothing's definitive one way or the other, actually."

As Cinema Blend notes, Feige's response could mean the character will be needed for an "Avengers 3," or heck, maybe he will just find his way into the sequel, anyway:

"What's interesting about Thanos is that villains get no bigger than him. So if the Avengers face off against him in Age Of Ultron, what do you do for a potentially trilogy-ending third film? Part two not only sounds like it will belong to Ultron, but it also sounds like Ultron's not about sharing the spotlight with any other villains. Then again, Marvel tinkers with their films until the very last minute, so, again, Feige is being coy when he leave open the possibility that Thanos might show up and at least talk in Age Of Ultron."

"Avengers: Age of Ultron" stars Robert Downey Jr. (Iron Man), Chris Evans (Captain America), Mark Ruffalo (Hulk), Jeremy Renner (Hawkeye), Chris Hemsworth (Thor) and Scarlett Johansson (Black Widow). Other actors featured in the film include Cobie Smulders (Maria Hill), Aaron Taylor-Johnson (Quicksilver), Elizabeth Olsen (Scarlet Witch), Paul Bettany (The Vision), Samuel L. Jackson (Nick Fury), Andy Serkis and James Spader (Ultron).

"Avengers 3" release date is still, obviously, a long way away, check back often for updates.