Easyjet are currently in a vulnerable position with Brexit hanging over them and (in theory) legal trouble around long term traffic rights. Easyjet's legal team will be doing all they can, but management will be aware that a magic wand may not solve everything, especially if a competitor airline decides to challenge Easyjet's view of the legal world through the courts.
That said, a company would need to have very significant resources to mount a takeover bid of Easyjet. I doubt a company outside the UK / EU will be able to get round legal ownership constraints. Furthermore, other major airline companies like IAG, LH or AF-KL will be aware of the difficulty in integrating a LCC with a full service carrier without destroying company culture and invoking labour strife. A bid from Ryanair may well raise monopoly/competition concerns.
If I was a CEO thinking of bidding for Easyjet, I would want a much better idea as to what Brexit is going to look like from a legal standpoint first.