T-Mobile has updated their Sidekick customers about the Data loss and service disruption that occurred last week.
T-Mobile is giving Sidekick owners some hope that their data will be recovered. T-Mobile says that recent efforts indicate the prospects of recovering some lost content may now be possible. I'm not sure what this means, but it's possible they are using low level disk data recovery software to restore the wiped out data. T-Mobile will continue to keep Sidekick owners updated on this front.
If your Sidekick data is permanently lost you will know when you get a $100 customer appreciation card that you get in addition to the free month of data service that already went to Sidekick data customers. This $100 card can be used towards T-Mobile products and services, or a customer’s T-Mobile bill. For those who fall into this category, details will be sent out in the next 14 days.
Via this T-Mobile statement.

There was some talk about Sidekick customers get the choice of new discounted phones, but the official guidance now is that you get a $100 gift card if the data on your Sidekick is really lost.