I don't think I understood your question, but I want to respond anyway.
1) Votes thar are not cast evaporate into the ether after twenty-four hours.
2) Asking where the "surplus" votes go is meaningless; votes have no existence until they are cast.
3) $NORM depends on both the number of votes cast and the number of posts made. $NORM is defined (I think) as the average reputation of the nodes created in the last week. In other words,
(++ votes on nodes < one week old) - (-- votes on nodes < one week old)
(nodes posted in the last week)
If the number of votes cast and the number of new nodes created both rise at about the same rate, the $NORM will not change much. On the other hand, the extremes (nodes with the highest and lowest reputations) will tend to become more extreme. This is just the nature of statistics*
... Which brings me back to the original point. Though it is true that the highest rated nodes this year will (likely) have a higher reputation than the highest rated nodes of years past, I don't see how it matters. There is not a "highest rated node of all time" only highest rated in the last day, week, month, or year. Any effect of increased voting will most likely wash out over all periods but the last, and even the yearly list should not be affected too much. (In my untutored opinion.)
*Which is not to say that I understand it in any deep way.