Off hand I'd think it "very small", as it requires both a future in which people (or their continuations) are around, and that significant power is held by a group (however large) who thinks we should reward and punish people as such, and/or have successfully precommitted to do so.
Also, suppose that there are and will be 1000 singularitarian activists who can, together, increase the probability of a positive singularity outcome from 0.1 to 0.2, and you are average amongst them. The benefit that accrues to you if you spend time working with the singularitarian movement is then delta U * 0.1/10,000 = 10^(-5) delta U, where delta U is the utility difference between the expected utility of the life you will live conditional upon existential disaster (which won't occur for quite a while - at least 15 years from today) and the utility of ...
I've been talking to a variety of people about this recently, and it was suggested that people (including myself) might benefit from a LessWrong discussion on the topic. I've been thinking about it on my own for a year, which took me through Neuroscience, Computer Science, and International Security Policy. I'm hoping and finding that through discussion, a much greater variety of options can be proposed and considered, and those with particular experience or observations can have others benefit from their knowledge. I've been very happy to find there are a number of people seriously working towards this already (still far fewer than we might need), and their deliberations and learning would be particularly valuable.
This is primarily about careers and other long term focused efforts (academic research and writing on the side, etc), not smaller incremental tools such as motivation and akrasia discussions. Where you should be applying your efforts, now how (much). Unless there's a lot of interest, it might also be good to otherwise avoid discussions on self-improvement in general and how to best realize these long term concerns, bringing those up elsewhere or in a seperate post.
A few initial thoughts: