Question:

If all the righteous people in Heaven will come back to life, does that mean that Heaven will cease to exist?

Answer:

In the Messianic Era, the righteous will dwell in Gan Eden as souls within bodies.

The Talmud states:  "In the future, G-d will make a dance with the righteous and will sit amongst them in the Garden of Eden.  Each one will point with his finger (at G-d) and say 'this [is our G-d],' as is written in Isaiah (25:9):  'On that day it will be said, behold, here is our G-d, we have place our hope in Him and he has saved us.  This is G-d in whom we have placed our hope; let us rejoice in his salvation.'"  This statement in Talmud indicates that with the dawn of redemption, when all souls in Heaven will arise and become enclothed in bodies, the Garden of Eden will still exist.

It is commonly believed that Gan Eden is the abode of souls after death.  However, the Lubavitcher Rebbe points out that one of the innovations of the Messianic era is that the righteous will dwell in Gan Eden as souls within bodies.

In fact, Gan Eden was originally intended for souls within bodies.  Adam and Eve, when they were created, dwelled in the Garden of Eden, until they were expelled because of their sin.  After eating of the fruit of the Tree of Knowledge, their bodies became less refined and were no longer fit to live in the Garden of Eden.

When Moshiach will come, any lingering blemish that may have arisen from Adam and Eve's sin will be completely removed.  In fact, the human body will be even more refined than it was before the sin and expulsion.  Thus, we will once again be able to dwell in Gan Eden, as souls in bodies.