If you decide to use Kubernetes, you can be sure that this solution is feasible for many years for several reasons.
All major cloud vendors support Kubernetes providing out-of-the-box solutions for it.
Ahead Of The Game
Alternative container orchestration solutions are far behind k8s in terms of adoption, support by cloud vendors and their ecosystems. Even companies previously focused on competing technologies are now endorsing Kubernetes: Docker is offering Docker Kubernetes Service instead of just Docker Swarm solutions and Mesosphere changed its name to D2IQ to be more open for Kubernetes and not purely focused on Apache Mesos.
The Kubernetes ecosystem is growing incredibly fast and new products supporting different needs on top of the Kubernetes platform are being released every day.
Transforms With You
Kubernetes is also future proof from an individual perspective: If you expect your user base to grow even to a huge audience, you can be sure that Kubernetes can handle it because it is designed to support large, distributed systems and it was originally developed by Google engineers and backed by their experience in building scalable platforms like Borg. The same goes if your application itself grows and becomes more complex. And finally, if you want to switch your cloud vendor for some reason, e.g. moving from Amazon Web Services (AWS) to Microsoft Azure, you can easily find a very similar Kubernetes service from a different provider and Kubernetes itself makes such a switch relatively seamless preventing you from vendor lock-in.