Updates are often rolled out in waves, though, so you may not get a notification that an update is ready for your Streak at the same time as other users. But don't panic. You can manually check for an update at any time.
- Press the Menu button on your Streak.
- Tap Settings.
- Scroll to the bottom of the list and tap the About phone option.
- Tap System updates at the top. The stock web browser will open. If an update is available, follow the on-screen instructions to download/install it.
This method isn't foolproof, as there have been instances of some Streaks coming up empty, but it's the official way to check for updates.
Unofficially, there's always a way to get the latest version of the software onto your device. It may require a tiny bit of hackery, but that's part of what makes Android so fun, right?