Today, while many benefit from the past contributions of members of the OER community, the sustainability of the movement itself is directly related to the future health and vibrancy of new community contributions.
A thorny issue here related to contribution just in the case of higher education textbooks in the USA (obviously there are lots of other cases to consider): Currently, most US EDU textbook "contributions" are given to commercial publishers from individual students in the form of money (although shaped by instructor and institutional choices). To reshape this contribution flow, EITHER we need mechanisms for students to contribute directly to OER efforts (like SUNY's OER Services model, SLCC's OER course fee model, models where students actively create/revise OER materials via "renewable assignments", and others), AND/OR we need to shift contributions away from students and toward — most likely — institutions (like Tidewater CC's Increased Tuition Revenue (INTRO) model and others).