Should the series be rebooted, it would be set in the same multiverseIt would start in a new reboot "Earth Prime", but the multiverse itself would be the same one we all know and love, even if they don't go to the same worlds.
Their Earth Prime isn't our own.If they ever traveled to our world they'd be surprised to find themselves in a universe where their exploits are actually a TV show in this world.
Sliding isn't random.This is true of all fictional inter-dimensional travel. There might be an infinite number of dimensions but some sort of lock (in the case of Sliders probably based on the people) that keeps you in your corner of the multiverse. This would explain not only the extremely odd fact that the Sliders repeatedly land in worlds so similar to their own that they had their own sliders who made the same mistake at the same time. It also explains why whenever they pick up a new person they almost immediately come upon a double. More than that so many other things seem to happen the same way an alarming amount of the time, usually most of history is identical. To the point that people usually have the same names, same friends, same life. So much so that more that checking a squeaky fence was the test to see if this was the Home World or just very very similar. It's likely that there are a fixed number of dimensions you're likely to slide into. Of course this also means that losing or gaining a member might very well decrease your chances of getting back to the original dimension.