I agree with Valerie but I would add that you need to be carful with user data. If the upgrade involves a non-reversible format change to the user data that needs to be communicated clearly. There are large companies who are guilty of not explaining this issues and if a user intends to maintain an old copy of the software - perhaps on another device - or communicate with others who haven't upgraded (Adobe, Microsoft I'm looking at you) then they need to understand the data migration issue. You should also be careful of turning off access to user data after the migration cut-off date. This is particularly an issue for SaaS software models.
Migration is much easier if you use OS mechanisms for automatically informing users that updates are available, which should mean that you aren't reliant so much on social media or informational websites (including your own) to get the message out.