Delaware Senate Seat a Contest in 2010?

An article from The Hill shows that National Republican Senatorial Committee Chairman John Cornyn is hoping to "broaden the appeal of the Republican Party" and make some traditionally Democratic states battlegrounds in 2010. Cornyn wants to recruit very popular Congressman Mike Castle to run for the Senate in Delaware. Could Joe Biden's seat be vulnerable? Cornyn also suggests that he is hoping to get Florida Governor Charlie Crist to run for Senate.