According to F4WOnline.com, the latest understanding is that Randy Orton actually first suffered his shoulder injury last Friday, two days prior to the Over the Limit pay-per-view.
The report says that Orton suffered what, at the time, appeared to be a minor shoulder injury. He worked through the injury at a house show Saturday and apparently aggravated it further, but it still did not seem particularly debilitating or concerning. The bout with Edge at Sunday’s Over the Limit then pushed it over the edge, and he is set to miss a few weeks from the ring.
As has been reported, while WWE still expects Orton to participate in the main-event at Fatal Four Way, if it is determined that he needs more recovery time, the contingency plan is for Sheamus to lay Orton out prior to the match. The storyline would set up a summer feud between the two wrestlers.
— Daniel Bryan vs. The Miz is indeed being discussed for WWE Fatal Four Way, but it has not been confirmed.