Teleporters, warp speed, and utopian futures are fantasy. Cell phones were an inevitability.
Star Trek will only be remembered as long as the current breed of visual entertainment media exists. One thing Trek did get right is TV (and probably film too) does have a limited life span. Who knows when it will end, but it will be overtaken by something else eventually. Heck, it's only a matter of years before videogames completely overtake them as the dominant pop culture media.
Once they go away, Trek will fade from peoples' memory. The thing about those other "big boys" is they're literature. And reading is timeless.
Space based video games will probably be around and as long as there are video games, and Trek has already put it's stamp on that media. For instance without Star Trek there would be no Mass Effect. There are already some great Star Wars video games out there. Players in the future are bound to be introduced to Trek through them even if has gone away by then.