I hope secularists in Turkey will soon fight back and depose him.
I think this will be very difficult. He did crush the national coup easily at first and then he gave punishment to more than 10.000 persons and no one of the population said a thing. The population is from his side. Erdogan has sympathy from the population and as long as it will be like this no one will fight him back.
Well I guess he can throw all hopes of Turkey joining the EU. Welp, even the very existence of EU is now precarious with stuff like Brexit and right-wing movements gaining ground in Europe. Even if don't collapse it seem people there would definitely not want Turkey in. Some even blame Turkey of taking advantage of the immigrant crisis.
As for expulsion, that will happen when people become fed-up with Erdogan. They can't love him forever.
They need to focus on making it work rather than admitting new members. Although it may well be too late for this.