decompiling back to C++?

IMHO, you can certainly get something.... Is it possible to extract some high level constructs from the binary... And this information can certainly be presented as C++.... Now, you will certainly not get any variable name, no classes/methods, just plain functions (it may be possible to get some information for virtual functions, but everytime the method is totally resolved at compile time, the information will not be available)... I don't think information on structures can be automatically extracted...

So what you will most likely get is a set of functions (which is not likely to be the same set of functions/methods used in the orginal code), accessing local and global variables, with un-precise types (some types can be inferred when the variable is used with known functions, but a variable is mostly a memory location.. can be anything).
The interesting information that can be extracted is part of the high-level constructs used in the function bodys: loops, tests... Some research project are already capable of extracting such information, which is then used to perform some optimization directly on the binary.

Anyway, to answer the original question, i would answer yes: it is IMHO possible to decompile to C++... For the most part, you can write assembly and C in C++, so it's not a big deal. However, you will get something which is more C than C++, and which may bear only small resemblance to the original code. And doing that would already need quite some time....