Lyrics lookup
Movie trailers
and so on.
There's no need to upgrade. We appreciate your support if you do. There is a steep discount for people who have faith that something good will be coming, but you can wait until the middle of the cycle and pay a little more if you see something you want.
A lot of work goes into general support of existing installations. Updates for operating system changes, for example. Server support for CD cover art and track lookup, forum, licensing support, playlist upload server, and on and on. This costs us money. Your upgrade helps.
I've never looked carefully, but my impression is that most people who upgrade do so when the best price is available.