Personally, I think that it just makes sense that Jesus would have been referring to the heavenly resurrection, because the whole idea behind him coming to earth at that time was to gather the congregation of anointed Christians (the “little flock”), which would be formally established at Pentecost in 33 C.E. That’s what Jesus’ disciples were supposed to be looking forward to. The “great crowd” of “other sheep” wasn’t mentioned until the apostle John wrote about it later in his book of Revelation around 96-98 C.E. The “Jonadab class” of “other sheep” wasn’t even identified by the WTS until 1935.
So, I can’t imagine Jesus talking about the earthly resurrection at that time when he was talking to the Sadducees. That wouldn’t have fit in with this heavenly kingdom theme and probably would have just confused things.
As for the earthly resurrection, that would occur in the “new system of things,” which I understand is supposed to be a time eventually leading to the restoration of God’s original purpose for humans on the earth – which was to be fruitful and fill the earth (multiply) and enjoy everlasting life as married couples on a Paradise earth. Now, I can understand that eventually earth’s expanding population would have to reach a limit, but it just seems basically cruel and unnatural (perverted) for there to be people living single and denied natural affection and intimacy with a mate of the opposite sex for an eternity (while always observing the animals getting to enjoy humping each other, which are supposed to be lower life forms than humans).
The no-marriage, no-sex theory regarding the earthly Paradise just doesn’t make any sense at all. I mean, what would be the point?