Brand Fatigue won't really set in until Marvel releases a couple of duds. With the amount of money invested going forward I don't think they will let it happen. What I do see as an issue, is if they'll bother making more movies once infinity war is finished.
As this is a Civil War thread - I'll admit to being uncertain about how effective a film it can be. The comic version was told over the course of a year with dozens of comics included. How many more characters will really be around in the Marvel cinematic universe by then and how many of those will be fighting for screen time ?
Avengers 2 - Probably a sure thing at this point. Status Quo will be maintained. Box office prediction - 1 Billion + (70% from overseas)
Ant Man - A guilty pleasure spin-off, will neither tarnish nor excel the brand. Box office prediction - 350 million (50/50 split WW/NA)
Cap 3 Civil War - Uncertainty , if it's actually really good I suspect it will be on par with Cap 2's gross. 600 million + (60% overseas)
Dr Strange - A smaller film , the character isn't as well known and in the sea of competition I suspect it will get lost. Probably a safe failure though, if they lose a bit on this one it won't effect the larger whole. 250 million (50/50 split)
Guardians of the Galaxy 2 - I see great things here, guardians 1 was basically a nicely built fan version of star wars and I suspect the sequel will continue that trend. People really liked the first one and I think the second one will outdo it. It's lack of "super heroes" will save it from any kind of stagnation. 700 million + (60% overseas)
NEW spiderman film - this is going to get 2 years of promotion , not to mention the possible appearance in Civil War and I think it will be the biggest spiderman has ever been. 1 billion (65% overseas)
Thor 3 - I can see it maintaining the quality of the other 2 thor films, nothing more. 500 million (60% worldwide)
Black Panther and Captain Marvel - of anything that's been announced I'd be most worried about these getting cancelled. Word on the street is that , thanks to spiderman a handful of the newer properties got pushed back. Right now Avengers 3 is due out before either of these films but you'd think marvel would want to introduce these characters more formally to include them in the infinity war wouldn't you ? If they do make it out I'm thinking 300-400 million each worldwide.
Avengers Infinity war parts 1/2 - This one is a pretty safe bet, it will be made no matter what. The scope of who ends up being included in it is what could change. I'm thinking it will earn 2 billion world wide (between both films)
Finaly, The inhumans - this may be saved for post avengers 3 has a way to reboot the marvel universe. Or, much like black panther and captain marvel it could end up in limbo. If anything, since black panther is due to appear in civil war , perhaps his movie should still come out and captain marvel get's a delay until post avengers 3.
This way, marvel could make a NEW avengers with a different cast. Maybe toss out a she hulk film ?