In my opinion regarding the return of suspended roller coasters, I don't really think the concept is outdated, but it's too bad Arrow isn't around anymore to make swinging suspended coasters without floorless trains. The swinging suspended coaster concept is good idea for kids who just reach 48" mark and are still not up for riding the more thrilling coasters, but have outgrown kiddie coasters.
Suspended roller coasters can be marketable, if B&M, S&S, Vekoma, or some other company is willing to bring back old style suspended coasters without the floorless trains.