That’s great that you are getting into Flutter and liking it. In answer to your question, once we released the beta of Flutter it took off — even faster than anyone expected. Flutter is currently in the top 50 repositories on Github and there are now over 500 Flutter apps in the app stores. Monthly active users of Flutter are skyrocketing, so there will be even more apps soon. Alibaba (the largest e-commerce company in the world, even bigger than Amazon) is using Flutter in their currently released app, which has tens of millions of users. And we are busy finishing up the 1.0 release of Flutter.
You will find (as others have) that learning Flutter is fast, and I have no doubt that it will be around for far longer than 15 years. If you have any doubts, just look for the hashtag #flutterio on Twitter, or search for “flutter” on youtube.com or medium.com.
As you noticed, this article is almost a year old. That’s why I’m writing a new article about Flutter, to bring things up to date.