Did Jesus ever say that Heaven is the end?
...And what I mean is: Did Jesus ever leave open the possibility of reincarnation on Earth, another planet, or elsewhere?
The gospels do not specifically address the question, but the book of Hebrews does. It is appointed for men to die once--not many times. After that is the judgment--not one of many judgments--the judgment.
And inasmuch as it is appointed for men to die once and after this comes judgment, so Christ also, having been offered once to bear the sins of many, will appear a second time for salvation without reference to sin, to those who eagerly await Him.