Not really. 'Sly' collocates much better with 'smile' (or look, or glance or expression, and so on) because 'sly' suggests that the person knows something that you don't. If someone gives you a sly smile, you can be sure that there's a secret they're not telling you. Slyness suggests secretiveness: for example, doing something 'on the sly' means doing something behind someone's back. Wily, on the other hand, suggests cunning and cleverness, and the ability to manage situations to one's own benefit. All these characteristics - wiliness, cunning and slyness - are the attributes of the fox in traditional fables and folklore, but they're not exactly the same.

They are similary in meaning,but wily is more to describe an action.I don't think you can have a "wily smile" it sounds odd.I think that "a sly smile" is more of an idiom-those words go together well.