they should build a decentralized exchange directly into core client, no need a third party software
that would be majestic to have
That wont happen because it would add too much weight to bitcoin nodes.
The bitcoin daemon has only 1 purpose to run the network, and most nodes do only this.
If you want to trade, you will have to run a different server, like bitsquare, which is already standalone.
The same way if you want to do commerce you run openbazaar.
You cant integrate non essential parts into the core, because it would burden the nodes.