First off, God doesn't need 2000 years to build our mansions in heaven.
He can do this with but a word, and has already accomplished this.
Secondly, satan and the fallen angels have been expelled from the third
heaven where God dwells, and now reside in the first and second heavens,
below the third heaven.  Satan and his angels have no presence in God's
heaven as a dwelling place.  Satan and his angels are cast out of the
first and second heavens after war with Michael and his angels, and they
are cast down to earth.  This happens during the Tribulation Period,
probably near the middle of it.  The saints will be in the third heaven
when this takes place, having been raptured there prior to the beginning
of the Tribulation Period.  God has already prepared very special
mansions for believers, and they are not tainted by satan and his
angels, and they don't need to be remodeled.  Don't allow anyone to
convince you otherwise!  A marvelous surprise awaits us in heaven!

Wes K.