Eh, I'm sticking to a cap of 6. To me the intent seems to be 'even if any rule allows you to get extra Minors later on, you still won't be able to start your turn with more than the normal limit, so you'll never be able to perform more than 2 Attack actions during your turn'. It seems that originally it was 1 Minor per Initiative Die, given how surprised some people were to hear that it now is (1 per die) + 1. So the 5 limit would be from the original max 5, and it doesn't break anything if it's turned up to 6, without punishing people who obtain a fifth die.