Lazer has top priority for peppy and the team so there isn't much time to deal with managing osu! merch and the store.
However, restocks are planned, and a partnership was mentioned late last year with Tanggible for some new merch goodness. Items were sold at Twitchcon and there are plans to bring items to an online store, so keep an eye out. Hopefully all that will come sooner rather than later.