The Miranda issue is over. As Wells noted earlier, Tsarnaev made his initial appearance before a magistrate judge, at the hospital, and at that time the judge informed Tsarnaev of his right to remain silent and right to counsel (the transcript of the session is here, and the key passage is on pages 4-5). The Boston Federal Public Defender's office has provisionally been appointed to represent him, and without objection from prosecutors the judge agreed that defense counsel may have access to Tsarnaev at the hospital consistent with medical considerations (see page 7)--thus appearing to eliminate the prospect of Tsarnaev might be screened off from counsel.
So, what happens next on the interrogation issue?
It is certainly possible he will cooperate. Indeed, it is possible that this will be counsel's advice, given how overwhelming the evidence is against him. If it works out that way, so much the better.
It is also possible that he will not cooperate. In that case, the million dollar question becomes whether the government would attempt to conduct interrogations notwithstanding an invocation of the right to remain silent or a request not to be questioned absent the presence of an attorney. One hopes it need not come to this. If it does, there will be fierce criticism whichever path the government takes (and, presumably, much litigation if the government does attempt an intelligence-focused interrogation without counsel).