Face it, not doing a load test before steam is a plan for disaster.

I think a 10 day pass emailed to all active and inactive accounts would do the trick.  It would give a chance for the old guard to log in and hookup with old friends. Players will get excited! Bots will die! Some would start talking about rebuilding their gama's before steam.  New corps of vets would organize, assets would be liquidated on the market, Players will  buy ice, players will sell ice.  Accounts will get subbed-Some will stay and some will not., but~

The server will get needed load test, and there will be good fun for all.