No, rebellion is not going to be 64bit.
There are many problems which can arise from trying to make a 32-bit game 64-bit. For example
- The problem with 64 bit is that every single third party library used in the game needs to support 64-bit (must have 64bit version). Look into SoaSE installation directory. See all those DLL files? Every single of those must exist in 64bit version as well. These are usually provided by 3rd party vendors...who often don't provide such version (and perhaps some of these aren't in business anymore, so there is nobody to make such version). And that is not whole story...there may be even more 3rd party libraries "hidden" within the SoaSE executable (those are called statically linked libraries...as opposed to dynamically linked libraries). Those need to exist in 64bit versions as well.
- Another major issue is network compatibility. Objects in 64 bit version have a different memory layout than 32bit objects, which can cause issues during (de)serialization in network comunication. Another issue is that floating point in 32bit and 64bit processor can have different precision charateristing. This effectively means, that if you multiply two numbers on 32bit and 64bit processors, you can get different results. Do you see how that could cause issues?
And there are more.
All of these can be worked around, but the game must be designed with that in mind. Sins are not.