No, they may want to lock the source. Tho, you can run any modification you want, if you know how to do it. In 1.5 it was a hell harder than it is today. So seeing people complaining about being hard to put a mod because you have to move stuff through folders, give permissions, and use a terminal, make me incredible nervous.
Still, I highly doubt they will lock the source. Android growns due the freedom of its open source. So no, it will stay opened, what the OEMs does is problem of the dumb people who gets their devices because they want a trademark logo instead of a good device.