FreeGameDev

I lilke to play STK though I have poor skill...

Nowadays I want to play games with my friends. STK is easy and interest. But it is only off-line. I think STK online will be a great joy.

Is there any plan of online feature?

Welcome here. Yes, in fact it's underway. :-) It will take some months at least before we have a release ready with that, but it will be worth the wait.

You could have a look at the teaser:
http://www.youtube.com/watch?v=J8oTmEpDGss

But as Arthur said, it's still work in progress.