In season 7 Willow activates all the current potentials. Question is, what happened to all the potentials in the past that might be alive before Buffy? Did they cease becoming potentials when she was activated?

I think I know what you mean (that before Buffy was called she was one of many potentials, so when she was called did that take the others out of the running?). Hope I'm answering the right thing :)
If so I'm pretty sure they remain potentials, I think being a potential is something too special for a new batch to be made every time a new slayer is called.

When talking about the spell Buffy says something along the lines of 'anyone who could be a slayer will be' and I think that includes those who were potentials before Buffy. But I do think there's a chance there's an age limit on how long you are a potential (because I doubt there's ever been an old woman called as the slayer) so I think pre-Buffy potentials would have been made slayers, but perhaps only if they still physically fit the mould of potential, some of them may have aged out of the running.
That's the impression I got, but I'm not completely sure, it may have been cleared up in the comics which I don't read.

I don't understand the question... :/

I do definately believe they are still potentials. Being a Slayer is being someone with an extremely short life span. There is a lot of job turnover, so to speak. However the older the potentials get I feel the more "out of the running" they are.

Hmmm i don't think any potential in the past would have been activated after willows spell everything takes place from the current slayer now and in the future .there is no way willows spell could ever go back that far unless she was able to go in the past.

I don't think the spell would be strong enough to affect Potentials who had already died (though that'd be an interesting idea for fan fiction, if any of them had been turned into vampires). The spell affected the present and the future, not the past. I also assume there was a specific age range for the Potentials affected. I don't think any child Potentials would become Slayers until they'd hit puberty, and I think at a certain age (early or mid twenties maybe) they'd become too old to be activated too.