A little tardy to the conversation, but keep in mind the first Fighter's Pass was also paced out kind of strangely. The first half of the year had almost nothing outside of Joker's reveal in December, Piranha Plant in January (even though he wasn't a Fighter's Pass character), and Joker dropping in April. It wasn't until June that we started getting character reveals and releases frequently, with a season reveal and a new release every two months.
As such, while I'm hopeful for Fighter #7 and #8 to be revealed alongside the ARMS character, they don't have to be. The only real evidence we have is the fact we're almost a quarter into the time period where fighters can release and we have only have a teaser for Fighter #6. However, that's not much more than what we had at the quarter mark of the first Fighter's Pass. As far as we know, Fighter's Pass #2 could be extremely backloaded like Fighter's Pass #1.