If I understand your question, you're more or less asking if humankind is more moral today than it was in the past. That's kind of reminiscent of the ongoing argument over the virtues of Nature vs Technology, which is a can of worms.
As rs.29 noted, the whole idea of advancing morality goes out the window if we exterminate ourselves - a very real possibility. In fact, it could be argued that the entire planet is already slowly dying - overpopulation, habitat destruction, pollution, climate change, genetically modified food and on and on.
One could argue that the root cause of our environmental woes is overpopulation, which could be described as a biological, rather than moral, function.
Nevertheless, I think it could also be argued that people have less reverence for the environment that becomes an ever more distant memory as we lock ourselves in our urban cocoons. For some people, myself included, environmental morality is just as important as inter-personal moral values. I'd trade Christianity for some wholesome animism in a heartbeat.
But it isn't just about Nature. You wrote,
As the present generation is acting in a more and more moral fashion,
continuing the trend of previous generations, there is clearly an
objective pressure that over time will bring us to a moral utopia.
Seriously? I'd argue that we're moving in the opposite direction, with the rich getting richer and our civil liberties going out the window. Where was the moral outrage regarding Obama's murder-by-unmanned-drone campaign or the destruction of Libya? In fact, life has never been cheaper; over a million innocent people slaughtered in Iraq, and there has still been no justice.
We can add another twist with the question are the immoral ones a minority?
The Kyoto Protocol demonstrates the ability of people around the world to rally behind a good cause. But it also demonstrates the ability of a small, organized group of evil people to sabotage even the best efforts.
Looking at it from this perspective, we might argue that humankind in general has indeed advanced in terms of objective moral values, but we're being held back by a cabal of sinister power brokers who easily manipulated us through propaganda.
But this, in turn, is kind of a self-fulfilling prophecy: If people who are essentially morally objective are brainwashed into believing that the war on terror is genuine and we should invade Muslim countries, then haven't they effectively morphed into the very monsters we're trying to escape from?
The final twist in the plot may lie in the solution. If we want to live in a truly moral world, then it might be necessary to retain our moral objectivism but at the same time rediscover our warrior past and learn how to fight back. Gandhi's tactics may have worked in India, but they have no chance against the corporate sector or the military-industrial complex.
Regarding notable philosophers who have commented on moral objectivism - well, a lot depends on how you define the term. Morality is a huge part of philosophy, and it isn't hard to find philosophers who have noted the difference between objective and subjective. According to Wikipedia,
Objectivism is a philosophical system developed by Russian-American
writer Ayn Rand.
Whether or not Ayn Rand herself was a paragon of morality is highly debatable. I agree with those who call her a racist capitalist.