osu!stream's intentions were to create an osu! spin-off that was sustainable as its own kind of entity. It's not going to have any plans of having beatmaps made here being able to port over to osu!stream anytime soon. In fact, I believe development for it has been on the backburner for quite some time.
With the way the game is structured as well and also the inclusion of multi-hit and hold notes, it's also a different ball game.
If you want to import osu! maps to play on a portable device, you may want to look at osu!droid stuff. But that of course requires you to have an Android product.
