Like any decades long comic, or story with multiple versions in multiple media, there is always the chance that someone gets married then it gets undone/someone dies/etc. Including Xavier. That said, he's pretty much eternally a bachelor. He has had three major romantic interests:
- A very squick-y interest in Jean Grey. This was brought up when Xavier became one of the most murder-y villains in X-Men history, Onslaught, in the 90s, and back in the 2000's Ultimate X-Men.
Considering movie Xavier is in his 50s and Jean is now 16-ish, this will never ever happen on screen.
- Lilandra Neramani, queen of the Shi'ar. The Shi'ar are a galaxy empire, and in the comics they are the sworn enemies of the Kree (as seen in the Guardians of the Galaxy movie). At one point he fakes his death so that he could be her consort. He never becomes king, just lovers.
She showed up in the 90's "The X-Men" cartoon, during the Dark Phoenix Saga. Which is the rumored topic of the next X-Men movie, now that All is Revealed.
- Moira MacTaggart. An intense mutual attraction, these two were at one point engaged, only for Moira to break it off to go back with her abusive ex.
Xavier and Moira have maintained a very professional relationship, both keeping their emotions in check, in the comics and cartoon. In the comics, she eventually dies after being attacked by Mystique. She and Xavier hook up once more before she dies. Yep.
In the movies, the plan as far as we know, is only to keep the Xavier and Moira relationship just barely on the top.
Movieline: Oh, yes. Moira and Xavier have a famous romantic relationship in the comics. How much of that relationship will we get to see?
Rose Bryne: I think it's more of a hint than a full painting, or whatever the metaphor might be. [Laughs] But there's definitely a flirtation and an affection; they're allies, so from the start they're there for each other.
The recent movie does the same, with just a kiss and some knowing looks.