Ubuntu 11.10 supports multiarch so you can install both 32 and 64 bit
applications, but if you do an upgrade then it will upgrade 32-bit to
32-bit and 64-bit to 64-bit. You might try to re-install applications first
to 64-bit versions and then do an upgrade. It looks like a headache and I
would do a clean installation. Precise Pangolin is
still almost three months away and I would wait until closer to release
date to make the upgrade. That gives you time to consider what to do.