No they should not ever be released. Their crime was barbaric, hacking a complete stranger to death like something out of the middle ages.
Adebolajo is a dangerous product of his fundamental christian upbringing and conversion to muslim extremism. He is clearly a mixed up individual, remember he was reciting words from the bible when he was claiming the murder for Allah.
Can those years of christian and muslim brainwashing ever be mended? Is what he is now the finished product? Sadly, I doubt any rehabilitation in the many years he will be in prison will rectify the damage to his personality.