Actually you're right and wrong :) (imho)

Yes composer is not updated, see:
https://travis-ci.org/ezsystems/ezpublish-community/builds/23508963#L30

No because travis will take care of that (afaik) 
And also to make in every PR/commit an extra 30s~1min or so, will be wasted time, since normally the old composer can do the tasks needed for this.

But I'm not an expert on this, maybe @andrerom @lolautruche @bdunogier can tell us more about this?