I’m sure you’ve heard the news by now: Teams and Skype for Business will converge into one. Here’s the official blog post: https://blogs.office.com/en-us/2017/09/25/a-new-vision-for-intelligent-communications-in-office-365/
And other articles for reference:
Could we add all the Skype function into Team, so I don't need to open 2 applications at same time? I do like Team more.
Skype has it's advantage like easy to find people to chat, and desktop sharing, etc. I hope you can combine them into one app.