I seriously doubt that we will be able to sin in heaven. I think people will be able to do as they please, but sinning will not be an option. It would be too complicated to send people who are already in heaven to hell, so I doubt God will give people that option.
In Heaven everything is supposed to be perfect, therefore meaning that there would be no reason for sin to exist. Heaven is a place of Godliness and sin does not exist there. According to Revelations, in Heaven, there will be no more death, sorrow, crying, or pain. If these do not exist, then there would be no sin. Everyone would be calm and happy.
This is coming from a Catholic point of view. In order to get into Heaven, you have to have a clean soul, no sin. If you have sin, you go to purgatory to atone for those sins. (as long as they are not serious sin) If you break one of the commandments, you go to hell unless you ask for forgiveness. Long winded, right? My point is, if you got to Heaven in the first place, you are without sin...so why would you even think about sin in Heaven?
There's a very good reason to believe that we will be unable to sin in heaven. That is, heaven isn't real. There is no evidence to suggest that our conscience will continue once our mind and whole body dies out, for what we call ourselves is our body. So no, you won't be able to sin because you'll be dead!