"If the Queen's head is taken off the stamps I will know that the lunatics have finally succeeded in taking over the asylum".
Why should it be such a lunatic thing to do? Not all of us are as mad for the monarchy as you seem to be. It seems to me to be a perfectly legitimate point of view or at least as legitimate as many posted on this forum.
As I said earlier, Royal Mail will make the final decision about this, but leaving aside ordinary stamps they print almost half a billion Christmas stamps every year, and that's likely to continue.
I can see no valid reason for discontinuing the use of an image of the monarch's head. It was mooted in 1965, and nothing came of it; I would be surprised to see it happen now. It might seem a small thing, but lots of these small things add up to a big erosion of our unique British identity - a hefty shove in the back that will accelerate a decline into mediocrity.
We have lots of reasons to feel proud of our country - why set about dismantling them one by one, simply because we can?