If the intent at the time of application for a HELOC is to purchase a new dwelling that will become the borrower's primary residence and the HELOC is secured by the borrower's current primary residence, should the HMDA Occupancy for the applicant's current residence be reported as Secondary Residence since the intent of the funds is to purchase a new primary residence some time in the future?

Sounds like a HELOC is being used as a bridge loan which would imply the FI cannot reasonably contemplate repeated transactions. I would be more concerned with the following in 1026.43:

(h) Evasion; open-end credit. In connection with credit secured by a consumer's dwelling that does not meet the definition of open-end credit in § 1026.2(a)(20), a creditor shall not structure the loan as an open-end plan to evade the requirements of this section.

Official Interpretation
43(h) Evasion; open-end credit.
1. Subject to closed-end credit rules. Where a creditor documents a loan as open-end credit but the features and terms, or other circumstances, demonstrate that the loan does not meet the definition of open-end credit in § 1026.2(a)(20), the loan is subject to the rules for closed-end credit, including § 1026.43.


However to answer your question IMO you report it as the principal residence securing the HELOC.