People will.
Have you ever done anything just because you wanted to do it? Not because somebody paid you, but simply because you wanted it done? That's what I've been talking about - there will always be people who will be curious enough to continue pushing sciences further and further. Besides, there are non-material benefits that will remain - respect of others, for example, taking pride in your own work, etc.
There will be a choice - to work and get everything and not to work and get the same. Some will choose not to work, but there will be plenty of others.