My guess is that the upgrade success rate will be pretty good for Titaniums at least this first year because:
1. We're talking about a grand total of two routes (SEA-LHR and SEA-FCO)... maybe SEA-KEF as a third?
2. These are new routes and AS doesn't have the name recognition (at least not yet) for trans-Atlantic flying.... cabins are likely going to be far from full for awhile.
3. Many travel overseas with at least one companion which means those Titaniums will get skipped over if their companion is on the same PNR.
4. The cash or mileage cost to upgrade isn't really competitive right now...my parents got a main cabin ticket for SEA-LHR in September and would probably cough up some $$ for an upgrade but not $3000.