If this is a concern for you, i.e. will SearchMonkey, BOSS, Site Explorer and so on, be around in a year or two from now, then you should read on. In fact, Vanessa Fox covered these questions in detail at Search Engine Land.
To make a long story short, we honestly do not know. Yahoo doesn't know, Microsoft doesn't know, I don't know and you don't know. I can still see SearchMonkey, BOSS, Site Explorer all working with Microsoft's Bing, but will Yahoo continue to invest in those tools? I don't know. It is clear to me that Yahoo wants to cut most, if not all, of their spending on search. So if that is true, which I think is, then Microsoft would have to pick up the technologies behind those tools.
Will they? I don't know. I can honestly seeing all three of these tools being forgotten in two years from now. Maybe some form of "Bing" tool will come out to replace them, but will they replicate all the features? I doubt it.
The truth is, I don't know. If I had to guess, in two years, we won't have a SearchMonkey, BOSS, or Site Explorer. I am not sure if we will have something equivalent from Microsoft Bing.
Should we start worrying about it now? I am not sure if that would do any of us any good. Clearly, Microsoft is reading this and know that these tools and features are something that webmasters and SEOs treasure.
Forum discussion at WebmasterWorld.