Unfortunately yes. The Oregon Open Primary makes no new provisions for maintenance of minor parties, who can currently maintain qualification by polled voter support of candidates they nominate directly to the general election.
Fortunately there is a simple legislative fix for this problem. Concurrent with adoption of an equal voting method as required by the intent of the Oregon Open Primary, the Legislature can shift minor party qualification to voter support in the primary of candidates registered with a minor party. Because this voting system more accurately reflects the electorate's true support of minor party viewpoints, this will very likely make it easier for minor parties to maintain official minor party status.
Aside for making it easier to maintain party status, minor party and independent candidates will see an accurate level of support, where today voters face a strong disincentive to honestly support a minor party candidate. An alternative voting experiment that surveyed voters at polling places in Manhattan’s 69th State Assembly District compared plurality voting (vote for one) with a variety of voting methods including Approval Voting, with the following results:
While the district was clearly not representative of the overall American electorate, note the relative strength of minor party candidates compared to the major party candidates. For example, Green Party Jill Stein received one vote for about every 27 votes for Obama under Plurality voting, versus one vote for every 1.7 Obama votes under Approval Voting.