Another study appeared yesterday generally supporting active surveillance for low risk cancer.
https://jamanetwork.com/journals/jama/article-abstract/2819352?resultClick=1
Obviously this an individual decision, and there will be a lot of factors to take into account. It's all about balancing various risks.
For what little it is worth my own personal view is that the possibility of avoiding prostatectomy/radiation for a long time, and maybe even indefinitely is a prize not to be sneezed at.
Even in those cases where treatment is eventualy required, there are competing factors to consider:
On the one hand, as some have said, there is the possibility that the final outcome might be worse if treatment is done later.
On the other hand, however, that is only a possibility and will not necessarily be the case by any means. And in the meantime:
a. those extra years of life to be enjoyed without treatment could be very valuable
b. techniques of treatments may improve and there may even be better treatments coming along that aren't available now.