OpenSystems hardware has it for a long time, z/Series has it for quite a while now, so by now there is no platform NOT natively supporting 64-bit arithmetic.
So please introduce an I8 datatype into Natural - on all supported platforms (and NOC as well) - as more and more "external" systems deliver 64-bit data which can not be handled via Natural.
We will consider this idea positively to be implemented in the next releases.