I was thinking google made some type of comment about an upgrade/update support timeline for android phones so I did some google searching. Turns out it was only encouraging it, and not requireing it ('it' being an 18 month update commitment). Sprint is on the list in this article, but Virgin Mobile is not (I think it's owned by Sprint). Consequently, I conclude that there is no commitment to update/upgrade virgin mobile hardware.
Google encouraging 18 month update pledge for Android phones - that's encouraging, not requiring