We just had this question a couple of days ago. The run does not count. The runner from second was forced to leave second and remains forced to acquire 3rd as long as no runner behind him has been put out. That runner from 2nd could stop for an hour and if after that hour, the third baseman finally steps on 3rd or tags that runner, the run would still not count. A run can not score on a third out that is a force out. No matter how long it takes to make that out.
