One thing that will be truly generational for Millennials will be extremely high expectations. While all generations will have increasing expectations in the years to come, Millennials have been shaped by the technical revolution. They will continue to ask "why" and "why not" and will not tolerate the stupidity of the status quo but rather they will drive change for frictionless solutions.

In the social sciences it is common to find generational effects by controlling for two other types of effects. After confirming that there is a significant difference between age groups, we try to find if it is an age effect, a period effect or a cohort effect. An age effect simply finds that people who are born in different time periods have different preferences. E.g. if you first ask a group of 70-year olds and then a group of 25 year-olds how they like to spend Saturday night, the difference is mostly reflecting an age effect. The idea that Millennials are inherently more innovative is one of these confusions that are often made. All young adults tend to be early adopters, but this interest tapers off when moving into the next life phase. A period effect is a trend we are all subjected to, e.g. addiction to mobile phones. Young people tends to be more addicted, but we see the effect in every generation. The cohort effects reflect true generational differences because these are traits that persist in peer groups over time. Very few trends are either subject to only age, period or cohort - most of the time we observe coefficients, meaning that there are partial effects that reflect all these forces. But it's important to consider all of these effects when we make our conclusions.

Anne Boysen, your question reflects an insight that many others lack: that "Millennials" even today are not a homogenous group. Some are even now parents themselves, with different attitudes and needs than "younger Millennials". So, while it is convenient to think of them as a group, they and their needs/attitudes are far from uniform.

I think we should start with this as the basis for discussion, segment further as appropriate, and pose the question again.

the millennial trend that will "grow out of" is the trend that they are actually creating trends. this is not sustainable and will revert back to designers and retailers whom create trends.

the generational trend is the desire for customized and personalized products

Many trends that are attributed to Millennials are not even from them. We attribute them to that generation because they are large and are making waves in social media (which is considered the new media today). However, Generation X developed a lot of the technology they grew up with which in turn has changed how they live, work and play. Gen X on the other hand didn't integrate with technology till they were in there 20's and 30's and didn't grow up with it. Gen X is a smaller population and we are mostly forgotten but we also have a smaller percentage of folks who can make waves and look like trends in the media.

There are trends that Gen X have started that Millennials are catching on to. There are many in Gen x that are living nomadic lives or that took gap years after college. We attribute that to being a Millennial trend which it is not.

As someone mentioned above even within Millennials there is such a wide divide on how they live, work and play based on their time in their journey of life.

We need to start looking at trends from a human perspective and not just generational. Living longer, healthier, smarter is making trends that are relevant to all generations and in actuality we are not looking at the trends that are critical because we are living longer, healthier and smarter.

As mentioned by Dawn expectation is truly generational for Millennials but when they face issues to meet with these then look for different opportunities through their own channels. Mobiles and social media are the gateways to access contents over the web, to be successful you need to be mobile friendly now. Influencer, blogs and youtubers are some of the main communication channels to create trends, live video could become viral to create new discussions.

Our generation feel that we are special and privileged because we are pampered by the previous generations.. We are achievers and competitive, hence we are likewise pressured due to the high expectations the previous generations have on us.. We have or own brand, We like products that would suit traits and personality, make things easy for us, like automated machines, etc, high yield products and financial solutions.
We will outgrow being dependent and too demanding

Some studies contradict the typical cliche that the generations are different. Due to this, it is less that Millennials are different, but that all generations today changed. It is not only the younger generation, which has higher claims and spends more time on the smart phone. All generations do so.