don't think they could use the same character given they would have tie it pretty closely to the events of FO3 or NV
No, for different reasons. Fallout 3 isn't tied closely to any of the other Fallouts, so Bethesda is either going to tie Fallout 4 with Fallout 3 (The first Fallout game they created), or put it next to the series, and try their best to stay true to it.
While I think the east coast is neat, I hope Bethesda stays true to the series. If they do so, it means that Fallout 4 will tie in more closely to New Vegas and Fallout 1+2.
(They're going to give the new protagonist an entirely different Alias, and it won't have anything to do with the Lone Wanderer, Courier, Vault Dweller, or Chosen One).