The IFRAME element is part of the upcoming HTML5 standard. Also, HTML5 is developed by the major browser vendors out there (Mozilla, Opera, Safari, IE), that basically makes a guarantee that we will have an IFRAME element in the foreseeable future. Some of them have support for some HTML5 elements already, like AUDIO and VIDEO and some new JavaScript APIs.
It’s also true that the OBJECT element is in the draft, but that’s because IFRAME and OBJECT will have different purposes. IFRAMES are mainly designed for sandboxing web applications.
So, my advise is to use IFRAME instead of OBJECT.