With all due respect, this is a terrible argument.
Premise 1 reduced the value judgement of lives to a dichotomy. On what basis? Can't there also be mediocre lives? I also agree with James Ridley, a bad life may still yield decent things. Many artists for example, like Vincent van Gogh arguably suffered enough to constitute a bad life. Should he never have existed? What if the person who cures cancer once and for all also had a bad life? Many people who suffer will often choose to suffer over not existing, there is a certain privilege, and honor in even getting to look at the sunrise. Would you rob this of the human beings yet to be (without asking them)?
Premise 2 is heavily contingent upon premise 1.
Premise 3. According to many religions there are rather measurable boundaries for a good life. It is true that they (and other, non-religious sources) present different, perhaps conflicting views about what constitutes a good life, but won't you consider the possibility that
a) There are multiple ways for a life to be good, not just one. There are multiple ways to travel from New York to Los Angeles, each with pros and cons with respect to cost, travel time, and safety. Does the existence of multiple paths make it impossible to travel from one place to the other? No.
b) The differences between different kinds of good lives are trivial. Even the stringent Catholics I grew up with often acknowledged that other religions were still doing things that contributed to fulfillment. I think it's also possible to do many of these things without religion.
Also if some lives are better than others, might it not be worth comparing the differences between these lives, and making an attempt to articulate the basis on which you qualify lives as better or worse than each other? Instead of doing what you do in premise 4, and basically make it a condition of your argument that it is not worth investigating the truth of premise 3.
Besides all this, from the outset, you limit your analysis to weather a life is good or bad. This is my biggest sticking point. What about words like fulfilling, honorable, interesting, vibrant, creative, productive, dignifying, enriching, challenging, variable, or enlightening (for instance), instead of something vague like good or bad? In myths, religions and stories, the human condition is often essentially articulated as a struggle. There is the clash of will against fate, the challenge of coming to terms with mortality, the question of integrating into a society or pursing one's own bliss, many similarly substantial and interesting questions that are powerful to explore can take place even if they are (somehow) qualified as something vague like "bad".
Don't you see? Like even if we just accept your argument can't we just make it in the opposite direction with equal merit?
1. A good life is worth living; conversely, a bad life is not worth living.
2. One should procreate if one cannot have reasonable knowledge that their offspring will have a bad life.
3. It has not been established what the possibility of a bad life is. The most that may be said is that there are lives, and that some lives are worse than others.
4. It is unlikely that such a possibility of a bad life will ever be established, given the lack of consensus so far.
5. Therefore, is it not possible to determine if ones' offspring will have a bad life that is not worth living.
6. Therefore, there is a possibility that ones' offspring will not and in fact cannot have a bad life.
7. Therefore, one should procreate.
Hopefully seeing your argument like this will help you see more of its errors. Like how between points 4 and 5 you just jump from it being "unlikely that such a possibility of a good life will ever be established" to saying that it's just "not possible to determine if ones' offspring will have a good life". What is the basis for this conclusion? Other than it sounds like you just want it to be true.
Again, I mean this with all due respect. Life can be difficult sometimes, I'll grant you that.