What is the maximum number of transistors that can be put on a standard microprocessor?

Question

As title reads. To be a bit more clear: I merely know that advancements in new processor generations generally involve a higher density of transistors placed on a given area to dome degree. I was wondering whether we can savely determine the maximum potential ahead for this increase in density without fundamentally changing the architecture of a micro processor, e.g. say the industry managed to make the most efficient use of the area possible as per definition of the laws of physics