It’s a good question, but I suspect Apple will maintain the paid offering (with a free trial). You could certainly argue they could and should make it free (paying for the music themselves), but I think they worry just as much about the signal that would send to the music industry. Something like: “your art is just a subsidy we pay to sell more devices” — which, when you think about it, isn’t far from reality. But I highly doubt they want to go in that direction so explicitly.
I’ve always known in my heart that Beats belonged with Apple.