Wouldn't you say that someone who isn't hardcore otaku would be put off in trying a hypothetical new Gundam series because they've been burned with 00 S2 and Age consecutively? That's a long time that Gundam has been mediocre.
I'm not denying the historical patterns of Gundam but Age's objective was to appeal to a new demographic and that flamed out miserably. But the fact remains that they can't keep going to the same well over and over.
No, because people actually liked Gundam 00, just like people liked Gundam SEED Destiny. Gundam is a very broad brand which attracts a lot of different audiences. Are the people who like Gundam SEED Destiny the same people who like Gundam 00 S2? Who knows. Are the people who disliked Gundam 00 S2 the same people who disliked Gundam AGE? Uncertain. Are the same people watching every installment of Gundam? Definitely not.
I would say it's more likely that Gundam AGE performed extremely poorly because no one was really interested in it, as opposed to people watching it all the way to the end and getting really pissed off. In this event, it would simply mean that Gundam AGE failed to capture an audience. As such, there is no longstanding damage to the overall franchise brand, since it is a single component of the franchise which had no cachet whatsoever.
Let's not forget. The Gundam 00 movie did pretty well, so the idea that "Gundam fans" are getting burned one series after another is simply not true. The people who are most displeased with stuff like Gundam SEED Destiny and Gundam 00 S2/Movie are likely the same people who are rather content with Gundam Unicorn and looking forward to Gundam the Origin. They are likely also the people who are playing Gundam Extreme Versus.
The thing about the Gundam brand is that it is so wide, it caters to a huge range of age groups and tastes. Just because there is a vocal group of fans who dislike one part of the franchise does not mean that part is unsuccessful. Gundam AGE is definitely unsuccessful, but it won't have much impact. It only shows that there isn't much potential in building a serious Gundam series targeted at kids.
Let's not forget that Turn-A Gundam is also a financial failure even though it was critically acclaimed. Gundam X was also suffering from awful ratings and had low interest, so much so that it was cut short from the planned run. These all happened over a decade ago. The Gundam brand hasn't suffered from it.
Part of the risk of trying different things with each series is that success is not always assured, but at the same time, by diversifying the brand it also insures against a failure having impact on the other more successful parts of the brand.