Yeah, "FUCK" pretty much sums up the volume. (don't read further before reading to 723)
I think that this is a good development though. If Ippo went ahead and had a match with Miyata, he'd retire afterwards and the manga would end. I don't think the story will end on a low and depressing note after so long, so this means that Ippo will continue boxing and learn how to climb over this new wall in his path - the prospect of no longer having a clear goal. Lots of people become lost during their lives and by addressing this issue seriously in his work, Morikawa (the author) will connect will with many of his readers and create an interesting story - if exectued well of course.
Taking care of your parents isn't something to be lightly passed over, but I don't think that this will be the message that Hajime no Ippo will send out. Discovering and pursuing your own goals will probably be the direction that Ippo and the story moves towards.