There is not ETA, or anything even remotely close. The word is that there is a "possible" solution for the "old" baseband (not the current one that comes with 4.1) that it is only compatible with "some" devices (not details at which are those devices, people speculate that it is the 3GS, no one really knows). Nothing will see the light of the sun until maybe 4.2 after it have been Jail broken officially.