Enrico,
This has been discussed. If you do a search that thread(s) will come up. However, I believe that the short answer was that this will not occur in 13, but they are working on it. Perhaps we will see 64 bit support in 14.
Erich
AC 19 6006 & AC 20
Mac OS 10.11.5
15" Retina MacBook Pro 2.6
27" iMac Retina 5K