I've written about The Inhumans, stating (half tongue in cheek) 5 Reasons The Inhumans are Boring, and while part of that article was tongue in cheek, the group has never succeeded in carrying their own title for longer than a year. On the sales meter, they seem to fall somewhere in between Agents of Atlas and The Runaways. So, with that in mind, here is what I think Marvel will do to make the team more appealing to modern readers:
Disclaimer: Many of the suggestions I'm going to put forth are not the sort of thing I would like myself, but my sensibilities are out of touch with current trends, so that's your fair warning.
One: Kill off some of the old crew and introduce some new blood.
There are just some members of the old guard that are a bit quaint by todays standards. Ditch Gorgon, Triton and Karnak in favor of the new Ms. Marvel and a few other younger characters. Killing them off is a much better solution than just putting them in the background and focusing on the newer characters. Nothing says This story is important! than a few deaths here and there.
Two: Put the female characters front and center (in the way that modern comics are so good at.)
Three: Make all the characters talk like 20-something coffee shop patrons. (A tactic that's worked so well the Avengers...)
Hahahha! It's so funny! Carol Danvers who used to be an officer and Security Chief for the United States Air Force talking like a ditzy wallflower. That's what I'm talking about!
I'm pretty sure if Marvel follows the tactics above, they will end up with a comic that is every bit as successful and enjoyable as many of their other top-selling comics.