Assuming its a UFC fight next, Conor will fight khabib next. 3 reasons.
1. Khabib least likely out of all possible opponents to knock him out. If you pay attention to things Conor says, the thing he fears the most is getting knocked out cold. In terms of health reprucussions and loss of reputation. According to him BJ pen still fit to fight because he was never knocked out cold, and Conor thinks he never really lost a fight because he's never been knocked out. He also often mentions other things related to taking damaging shots.
2. Already lost to khabib, another loss leaves him in same position, a loss to a different opponent and he loses credibility.
3. Likely biggest payday
The only other possibility is sleezebag Ali gets Justin to agree to lose, so that he can get another big payday from mcgregor without ruining the khabib rematch.
There is ZERO chance he fights masvidal or usman, anyone entertaining that idea are fricking idiots. Mcgregor would get knocked out and fast. Don't forget he almost got knocked out by Diaz, Mayweather and Khabib, 3 people known for NOT knocking people out. Imagine what Masvidal would do to him. Someone just as tough as Diaz but with more power, better movement, better fight IQ.
Conor said he would fight before the summer to Ariel.. "I'd say so yeah, possibly yeah, yeah I would yeah, yes".. So basically No, he has no intention of fighting before the summer. He will wait until Khabib fight is there, likely after September.