Kent has noted that, on the current uncertain state of the law, prosecutors would be taking a risk if they use Tsarnaev's (presumed) silence as evidence of lack of remorse. I concur. But there's more to this story.
At first, I agreed with the conventional wisdom that defense counsel would not call their client to the stand. Now, I have my doubts. The government's evidence of the savagery and cruelty of this crime in my view makes the death penalty likely unless the defense can move the ball.
I think their best shot to avoid lethal injection is to call Tsarnaev and have him show remorse. If he does so, and makes a convincing showing, I think he lives. It would help if he broke down in tears of grief in a way that struck the jury as sincere, and not a coached performance.
And there's the rub. I have seen not a lick of evidence that Tsarnaev actually feels any differently than he did the day of his capture. That afternoon, he scribbled a note to the effect that he was in a Holy War against the United States, and if there was "collateral damage," in the phrase made immortal by his fellow butcher Timothy McVeigh, well......tough.
My guess is that it will depend on defense counsel's assessment whether Tsarnaev can pull it off, and that he won't break out in an anti-American diatribe during cross-examination. Having to make judgments like that is one of many reasons I'm happy I did not become a defense lawyer.

Not arguing lack of remorse based upon his decision not to testify is one thing. But arguing lack of remorse based upon his post-crime non-verbal conduct is another.
http://www.cnn.com/2015/04/23/us/tsarnaev-boston-bombing-sentencing/
Do you think he will take the stand?
Thanks for the link. CNN's coverage has been the best of the networks.
And, yes, cute little Dzhokahr doesn't look so cute when he's giving the finger.
I don't think he will take the stand, at least to be remorseful, because well, he isn't remorseful.
It appears his primary counsel is a master at weaseling convicted murderers out of the death penalty, so I'm sure she has some sort of plan better than putting him on the stand.
Absolutely will not testify. Remind me when I am wrong.
No argument there.
If he testifies and gets the DP, he'll claim later it was ineffective assistance to call him, on the theory that defense counsel had to have known that he would show his true colors and cook himself.
If he does not testify and gets the DP, he'll claim with equal fury that is was ineffective assistance not to call him, on the theory that the gruesomeness of his murders was so well established that defense counsel had to have known that his only hope was to make a display of remorse.
It must be wonderful being able to know that, whatever happens, it was someone else's fault, especially your lawyer's.
I doubt he will testify, it is too high a risk proposition for him to face virtually unlimited cross examination.
The decision to testify or not is wholly in the discretion of the accused. The only way this issue makes it into a Habeas petition is if the defendant claims his lawyer prevented him from testifying against his wishes. There will unquestionably be a claim of ineffective counsel in this case, just not on the grounds you suggest.