Fox did Marvel a favor by making this look so unlike FF. It will be very easy for Marvel to differentiate themselves from this film if they choose to do so.
And they'd also start by building enthusiasm with people like us. I can almost guarantee that if Marvel shows up to next year's Comic-Con with a a big

logo and 2020 date, nobody will be saying: "Again?! Another FF movie?!" with disappointment or disdain. They'll be thrilled.
Fans will be excited and it will build from there.
Most people don't have a clue who the Inhumans are, but once they start seeing trailers, they'll get interested. And I don't know why people would be less willing to see a well-done FF film with a trailer that shows some really cool things than they would be to see something like Inhumans that they've never heard of before.