On the one hand, we could argue that Jonson offers up what's considered a very traditional (and very Shakespearean) kind of ending for a comedy, which will usually end with a marriage or the promise of one.
(In a lot of Shakespeare's comedies, marriages are supposed to be a signal that all is well in the world and that social order has been restored. Go read the ending of The Taming of the Shrew for more on this.)
So, it's tempting to say that this is basically what happens when Master Lovewit returns to his home, restores order to the place, and marries the rich, young, widow, Dame Pliant. (Dame Pliant's name, by the way, might suggest that she will be a very compliant wife.)
On the other hand, we could argue that Jonson's giving us an ending that complicates and calls into question the idea that marriage is the signal that social order has been restored and everyone will live happily ever after.
Here's why: Master Lovewit's unruly butler has been totally running amok while his master was away. But, for some reason Lovewit decides that his servant is so amusing and witty that he's going to let him keep his job, especially since the guy can help make him some money.
Obviously, Lovewit is pretty confident that he can keep his butler in check.
But is that really possible? In the end, we're left wondering how things are really going to turn out at Casa Lovewit. Will clever Jeremy/Face and Master Lovewit band together and find more ways to swindle innocent people? Maybe. But, are we really supposed to believe that Jeremy/Face is going to keep his hands to himself when it comes to his master's hot, new bride?
After all, Jeremy/Face's totally into Dame Pliant, who doesn't really seem to mind which guy she ends up with. (Maybe she's the kind of person who will be compliant with whichever man is into her?)
In other words, is Jonson suggesting that Master Lovewit's just another chump who is going to get duped by his servant like everyone else (and cheated on by his much younger wife)? If so, then social order really hasn't been restored at all and we're left with a pretty untidy ending. (This, by the way, is fine by us.)