People come and go here at their own choice and for many reasons.
Most who leave end up by drifting back over time (I did !) and it's safe to say that the slightly addicitive nature of the forums acts as a real lure to anyone who has been involved with it.
I think it's safe to say that anyone who leaves will be missed, especially someone like Pops who actively contributed a great deal to the forums.
Such is the changing nature of this site though: as one person leaves, dozens of new members join and there will always be people here who will try and help out.
I certainly don't think that there is a general underlying current here that is set to affect us all and I very much doubt that you will see people leaving in droves.
All we can do is wish those who leave our best and carry on with doing what this forum does best.