Dell UK just announced on its official Facebook account that it will start pushing Froyo update to Streak users before the end of November. The update will start from UK and will be later pushed to other regions.
Dell also mentioned that it will be an OTA (Over the Air) update. It how ever did not commit any fixed date for the Android 2.2 rollout.
Update: Android 2.2 for Dell Streak is out, check out post here.