We currently have 35.000 active team members not part of Gridcoin
We have half a million active BOINC users and 4.3 million registered. And those are users who are running BOINC completely for free, paying for electricity and hardware out of their own pockets. Those numbers will likely increase even more, with Gridcoin covering most of the costs (or even yielding some profits). Of course, markets always settle in the end, but with millions of BOINC users available for recruiting, I wouldn't worry about it yet.
According to BOINC stats we have at this moment 175.000 active users. Of them around 35.000 are part of a team (not Gridcoin). When the mandatory team requirements disappear they can then start mining GRC without leaving their team. I don't really understand why we should consider 4.3 million registered users for BOINC altruistic specifically?
Number of active users is usually fluctuating between 200k and 500k. Will likely increase again as the winter arrives to Northern Hemisphere. For example, snapshot taken on March 25, 2017 shows 430.892 active users:
https://web.archive.org/web/20170325010254/http://boinc.berkeley.edu
Also worth mentioning, an active user is a user which has returned at least one result within the last 24 hours. However, many BOINC tasks take much longer than that, so it's a conservative number to begin with.
4.3 million users have shown enough interest in BOINC to install it on their machines, meaning they are considerably interested in computing for science. With a monetary incentive (Gridcoin), a significant part of them would probably become full users and are more likely to support a science-backed crypto, then a Proof-of-Work one.
Makes sense now, thanks for clarifying.