I disagree. if you have to built something up then take your time and don't rush it.
I think, what can be said now, that TA is the biggest commercially successful movie of all time (not counting anything Cameron did), is, that the audience for TA was bigger than the audience for IM. ittook 5 years and not only didn't MS lose audience in that periode, but instead they gave it time to built up hype.
A TA sequel in 2016/2017 could work exactly like that. new fans will be found on the road to TA2. look at all those crazy Loki fangirls who joined the party last year. if you have a charismatic character in the movies inbetween it will attract new crowd. again, a longer period between TA and TA2 gives more characters the chance to become the new Loki or Coulson in terms of fan appreciation and the hype will be bigger.
1) That's unfair of you to single out KangConquers' post, since it was made a year ago and long before he, you, I or anyone else expected Avengers to turn into the historical blockbuster it became.
2) It did *not* take 5 years for The Avengers to develop. Iron Man was released in 2008, and Marvel announced plans for Avengers to release in 2011 --- THREE years later. Writers strikes and Joss Whedon's schedule pushed the release back until 2012, but that's still *four* years, not five.
3) The first film in the Avengers franchise should naturally take longer to develop than its sequels, because you have to give the solo films time to introduce the characters, and time to develop the team. But now that the first one is out of the way, there is no conceivable reason to wait through Iron Man, Thor, Cap and Hulk sequels as steppingstones to Avengers 2 --- it's unnecessary, because the characters are already introduced, already well-known.
At best, the only thing you need to do is have a couple of solo projects for *new* characters to add to the team --- say, Ant-Man (which could conceivably introduce no less than THREE new Avengers, and possibly four --- Hank Pym, Janet Van Dyne, Scott Lang, and Vision), Black Panther, Ms. Marvel (again, multiple Avengers potentially), and Dr. Strange....or any combination thereof.
Avengers 2 should be due by no later than 2015. Any stalling beyond that will kill interest and hype, as KangConquers said.