The future! I can't imagine how anyone could say that. I started out with Smalltalk, then started doing C# professionally and eventually started doing CL in emacs. CL/SLIME/Emacs was by
far the worst of that trilogy. I can't think of one single thing that the emacs combo did better or even as good.
Both Smalltalk and VS+Resharper have great refactoring tools. Both have great debugging tools (and in Smalltalk I can even do a lot of development right inside the debugger and watch how the code is reacting while I'm writing it). In the CL/Emacs setup debugging is so bad most people recommend not to even bother; just use tracing. And I can't understand why it needs to be like this, CL is closer to Smalltalk than it is C# (that is, CL is a "live" language as Smalltalk is or at least it very much can be. Even a compile-only CL like SBCL).
The other issue is project management. In Smalltalk it doesn't really come into play as much since the image is your "exe", but despite this Smalltalk has great tools for organizing classes, methods and so on (and Dolphin's way of letting your image be a "solution" and you make individual exes from that that drop everything they didn't use was absolutely brilliant). In VS, I create my assemblies, make dependencies and so on and the IDE just handles all this for me.
Contrast that with CL/Emacs: CL has ASDF files that can manage all your dependencies for you (people complain about it, but I've used them for several years and never had any problems) but you have to manage all this stuff manually. If you want a nice way of saying "create new package" or "create a new file that is in this package" you'll need to write all that handling, UI, etc. yourself. And after you write it all, what will you have? The interface will be hideous no matter how you do it because you're restricted to just text. In Visual Studio you can have the disapearable side bars approach, the "old school mac" approach of different info windows floating all over the desktop, etc. With emacs you'd be restricted to doing that stuff via ascii art or popping up more windows with ugly ascii art in them.
The only way I could see CL/Emacs as the future is if we're talking post-apocalyptic.