At yesterday's event revealing the Droid RAZR M and Droid RAZR HD, Motorola also said that it would offer a $100 trade-in credit to those who bought a Motorola phone in 2011 (or later) that isn't eligible for the update to Jelly Bean. The company's trade-in page is now live and includes more details on how those owners left high and dry can get their $100 credit. RIght now, users can enter their name and email address and select one of 18 phones from a list to see if it is eligible for Jelly Bean— if the phone isn't eligible, Motorola will send out more details on how to get that $100 towards a "select new Motorola smartphone." Unfortunately, there isn't any detail on what phones Motorola won't be updating, nor is there any information on which specific phones eligible owners will be able to apply the discount to.
Update: This story originally stated that the Droid 4, Droid RAZR, and Droid RAZR Maxx were among the phones Motorola would not be updating to Jelly Bean. We've updated the story to reflect the fact that Motorola will be reaching out to owners to let them know if their phones are eligible for either an upgrade or a discount.