The future of the hidden iframe for uploading files

I’ve been using the older Valum’s ajax uploader and it actually works great. Although it only uses the hidden iframe technique for uploading files, I’m wondering if browsers may eventually restrict this functionality once the File API has a couple years to become the norm. Working with the File API is certainly a real blessing, but not by itself a perfect solution because of the need to support older browsers. I’m just wondering if my clients will eventually start calling me and telling me that the uploader script isn’t working anymore. What do you think?