I've taken the route of upgrading from 6.1.5 32bit to 7.0 64 Bit - This
worked without a hitch using the binary sets upgrading.
But pkgin decided to be a tad confused about the whole deal, I thought this
was due to some packages still being 32 bit, So I upgraded everything there
was to be upgraded, so now I no longer have any 32bit programs left.
You may need to nuke pkgin's database and regenerate it; I wouldn't be
surprised if it stored the host arch. But I looked at mine with
"sqlite3 /var/db/pkgin/pkgin.db .dump" and didn't see that.
Are you really sure that none of your installed packages are stil i386?
cheesy script:
$ cd /var/db/pkg && for i in *; do echo -n "$i: "; pkg_info -B $i | egrep MACHINE_ARCH; done