[whpalmer4]

You're making it overly complex. The easiest route is to simply put a start date on the action for when you want it to become active to alert you that follow-up is necessary. There's no need to assign it a special waiting context that is on hold, either. If you want more feedback that it isn't getting done, also add a due date. If Bob thinks he'll have a report on the new widget design for you on Tuesday, the action might be something like

Receive widget report from Bob @Agenda:Bob @Start Tuesday 8am @Due Thursday 5pm

The one advantage having a specific waiting context can provide that this approach does not is the ability to quickly see a list of everything you might be waiting on. However, if you actually put your waiting context on hold, actions which you are currently waiting for and actions which you will be waiting for in the future become indistinguishable because you can't use the available filter to sift them.

In any case, there's no built-in support for actions with automatically changing contexts. One could write an Applescript that walked through the database and made such changes and have it run periodically, perhaps as an alert action from iCal.