How hard can it be to move from a 16 bit architecture to a 32 bit architecture?
Yes, that can be tricky. Just one example that affects Java and BaseX: Java arrays are limited to 2^31 entries. Although 64 bit CPUs were getting popular a long time ago, I don’t believe this limit will ever be lifted in a future version of Java. Right now, we use simple integer offsets to address nodes in main-memory database instances. If we decide to introduce support for more than 2 billion nodes per database, we’d need to use additional redirections (which is possible indeed, but requires some more effort than replacing int with long values).
Maybe we could start a little new database project from scratch? ;) Various issues could then be solved more portable (but the switch to 128 bit architectures is probably still far away, so we could probably stick with 64 bit…).