Previous participants of this joyride: Japan, Korea, half of Southern Europe.
Reserves of cheap labor are not endless, and it's great that the capital actively seeks them out and eventually fills them in.
Let's not forget rampant corporate espionage, and deliberate IP infringement whereby designs used contractually to produce something, and then stolen to make knock offs as well.
In practice, in aggregate they are. As you mentioned, there were other countries filling that gap before, and there will be new ones. East Asia got there first because of a combination of factors (cultural, historic, and logistical), but once that area is spent, new frontiers will be opened. In fact, in markets where there are fewer logistical constraints (i.e. software), those new frontiers are already coming online (South America, Africa, etc).
Precisely because of this, globalization is destined to stay. It is the ultimate wet dream of capital: an endless reserve of cheap labor.
Marx might not have got the prognosis right, but his diagnosis still holds.