Domestically IM3, but not worldwide.
After The Avengers, IM3 saw a massive growth overseas, going from a 50/50 domestic/overseas split to 33.7/66.3 that wasn't just down to China. With TFA behaving like most previous Star wars films with a 45/55 split it would need to see massive overseas growth, and while Donnie Yen could certainly help improve the Chinese numbers, I'm not sure if they can do it.
"Security - release the badgers."

It will be just as hyped as Episode 7 was(maybe more-so, since 7 had the doubts of 'but the prequels sucked and people may not be interested')
It had the Disney make them really good and an interesting director going on for SW8 in Rian Johnson.
But it has to combat I think much stronger negative to achieve to reach the same SW7 hype.

1. First star wars movie in 10 year's vs third star wars movie in 3 year's.
2. What will it be ? It was vastly mysterious what they would be going for and what happened to the original movie character, now that is mostly gone except for Luke.
3. Sequel resistance, sequels has a lot of disadvantage going on, people that didn't see the first will not be interested, that said for no movie that didn't matter less than Star Wars, but you remove everyone that saw Awaken and didn't like it too. there is a reason that successful sequel almost never beat the original adjusted.
   But, it did happen for big successful movie sequel to beat the previous one:
   The Hunger Games: Catching Fire by only 4% (0.5% adjusted for inflation)
   Transformer 2 over the first (that I don't know what was going on)
   Pirates 2 over Pirates 1
   Shrek 2 over shrek (massive jump)
   Lords of the rings grew for every release, not in a small way.
   It does look almost impossible for Star Wars 8 or 9 (9 because it will be the sixth movie in a small windows), with how ridiculously big 7 was, but who predicted Awaken domestic success ? Not me

That's possible, but trends aren't necessarily law.
Before The Force Awakens, no sequel had ever become the #1 grossing film at the domestic box office. That was certainly a fairly well-ingrained precedent, that The Force Awakens didn't have an issue easily destroying.
Yes, the odds are high that Ep 8 and 9 will not match the domestic gross of 7, but I'm certainly not ruling it out. When you consider how successful 7 was, that it was generally loved by everyone who saw it, and that it had an ending that leaves one begging for the next chapterit isn't a crazy thought to consider.
It will be just as hyped as Episode 7 was(maybe more-so, since 7 had the doubts of 'but the prequels sucked and people may not be interested')and with the same release pattern, will have the benefit of all of the various holidays and long-weekends that Episode 7 ran into.
Self improvement is a full-time job

I think with Disney exploiting the Star Wars library if you will, the films will become less of an "event" film to see in theaters, with a potential of each film earning less and less than the one before it.
They seem determined to flood the market - something Lucas never did, with only six features in 28 years (a number Disney plan to eclipse in a third of the time). Worse, with the major reshoots, rewrites and additional directors on Rogue One it's clear that the original idea that the standalone films would be 'riskier' to attract quality directors has been thrown out the window once they saw how much TFA made and the films will be increasingly homogenised and formulaic, which will gradually whittle down their wider appeal.
"Security - release the badgers."

I'm not a Star Wars fan, so I really don't much about it, but you can make some simple comparisons with the original trilogy and the prequel trilogy.
Star Wars, the original, made the most money of the original trilogy. The Empire Strikes back was, I believe, perceived as an improvement over the first film, yet it had a sizable drop from the first, which continued with Return of the Jedi.
Likewise, The Phantom Menace did massive business in 1999, yet Attack of the Clones dropped from it. And although Revenge of the Sith saw an uptick from Episode II, it didn't match The Phantom Menace.
I believe we'll see something to this effect, in terms of domestic box office earnings, with this trilogy (if it is a trilogy). Force Awakens was massive; I think Episode 8 will be massive as well, just not as much as The Force Awakens was.
Also, I think with Disney exploiting the Star Wars library if you will, the films will become less of an "event" film to see in theaters, with a potential of each film earning less and less than the one before it.

I think Rogue One will be more equivalent to how Iron Man 3 performed relative to The Avengers.
I'm not positive about The Force Awakens necessarily being the peak. Of course, it is very easy to look at its staggering domestic number and say 'They can't do that again'. I'd say that is the LIKELY outcome.
But I don't think it would be impossible for another film to match it or surpass it. Star Wars is clearly just on another level than other blockbusters here in North America.
2017 is the 40th anniversary, they have the same beneficial release date, and I wouldn't be surprised if a roughly equal equivalent of people go see it. Heck, if it happens to be perceived as an improvement over The Force Awakens, who knows what could happen.
I don't feel Star Wars will necessarily wear down in the same way the Avengers franchise did. The Marvel Cinematic Universe was delivering 2 films a year, every film is essentially a sequel to what came before, and practically all of the Avengers were given their own adventures post-Avengers. So while it had been 3 years since we'd seen them ALL together.most had been seen in the interim.
Rogue One isn't telling us what Kylo Ren is up to in between Episode 7 and 8. It is entirely its own thing.
Episode 8 will be the first time that story is continued and all of those characters are revisited. There is appeal in that. The "Episodes" are still a huge deal and quite special in ways that perhaps The Avengers films aren't any more.
Self improvement is a full-time job

Closer to Iron Man than Thor, but not by much.