pg_upgrade and tablespaces (postgres 9.2 to 9.3)
PostgreSQL creates subdirectories named for the PostgreSQL version within each tablespace.

So AFAIK pg_upgrade doesn't need to be told to take special action for the tablespaces. It will use the same tablespaces as the original database, but won't conflict because of the use of different subdirectories within the tablespace root.

The caveat is that if you have tablespaces inside your 9.2 data directory, this won't work. You shouldn't do that in the first place. Move the tablespaces to a location outside the 9.2 datadir before doing the upgrade.