What i understand from your post you want to upgrade the database having streams configuration/objects.
so it would be consider as the normal upgrade method,during the upgrade process oracle only change the dictionary objects, not the object created by user.
The questions are:
1. Are the QUEUE table will be modified during the upgrade, altered or recreated?
2. Is there are requirement that all messages must be propagated and QUEUE tables be 'empty' before the upgrade?
When you run the preupgrade tool oracle give/suggest you all the information what you need to before upgrade
Yes, I would agree. The problem with streams/aq is that aq tables can be created in the separate schema, however the creation and all operations on these tables are done using DBMS_AQADM and DBMS_AQ packages which is the part of CATPROC component which is going to be upgraded to new version (and tables created with old version will be all over the rest of database).
Im just comparing the aq tables structures 10g vs 11g, and it looks like they are the same (except some minor stuff). So it looks like there is a good chance that streams will be ok. Again looking forward to test this soon.