is it possible for these bridges to forge gateways between parallel dimensions ala Sliders or is this a mere flight of fancy? Considering first one has to travel at the speed of light through such a vortex in the first place I know it seems highly improbable....but is it possible?

you answered your question..."highly improbable" which doesn't mean impossible.
But with current understandings the einstein-rosen bridges, aka wormholes...are purely mathematical adn there isn't really a way to test it with current equipment.