I don't think Mediafire is going anywhere as they do not have an affiliate program like the other companies that have been scurrying out of business these last few days.
However, to answer your question there are a ton of other file hosters in the marketplace starting with rapidshare. You can search on these boards for Many others but repidshare comes immediately to mind as an alternative to Mediafire.

Can I ask why you have been utilizing Mediafire over the other alternatives that have recently closed their doors like Filesonic, Fileserve, and others?