Good question! I haven’t heard any Rabbinical teachings about the upcoming census, but I can share a few relevant ideas and sources that should help give guidance in answering your question.
It's forbidden to count Jewish people. When they needed to count Kohanim (Priests) in the Beit HaMikdash (Temple), each one stuck out a finger and then they counted the fingers. Why didn't they just count the people directly? Our Sages explain: "Because it is forbidden to count Israel, as is written 'The number of the Jewish nation will be like the sand of the sea, which shall not be measured....'"
The concept is a mystical one: By counting, one is ascribing a finite value to a Jew, a number, a physical reality. In fact, the Jewish People is spiritually infinite, and should not be numbered and defined in the finite sense. Even when the Jews needed to be counted, such as the census described in the Book of Numbers (30:12), it was done indirectly, whereby each person contributed a coin and the coins were counted.
From the case of the Kohanim, however, we see that it's okay to count objects — e.g., fingers — which substitute for people. Moses counted the people through the 'half-shekel' that each one donated; King Saul counted them using lambs. Today, when counting the ten people required for a minyan, it is customary to recite the verse, "Hoshia et amecha..." (Psalms 28:9), which consists of ten words.
As far as the most recent Israeli census was concerned, Rabbi Shalom Yosef Elyashev gave the following reasons to permit participation:
- INDIRECT COUNT
As mentioned, it is OK to count objects - e.g., fingers - which substitute for people. In the Israeli census, it was not people being counted, but rather pen marks on a piece of paper.
- ESTIMATION
A large number of families forget, refuse, or simply don't bother responding. The census-takers fill this gap with government records and statistical guesswork (based partly on the number of doors in a given neighborhood!). Therefore, it is not a true count.
- INCLUSIVE
The Israeli census made no inquiry about religion. Rather, it counted Israeli citizens of all backgrounds and nationalities; therefore, it is not considered counting 'The Jewish People' per se.
- MECHANICAL MEANS
The actual counting was not done by humans; rather, the census form was scanned into a computer.
Based on all the above, Rabbi Elyashev permitted participation, but added that one should supply only the ID numbers but leave out the names. This was in order to emphasize the fact that the count is indirect.