Its not that simple as you described:

It never is :)

I don't think they should release Rebellion until there has been some experience with Land, as I reckon it would make the FOMO on a new set far greater, putting more pressure on buying packs, but also give the feedback on how Land operates, meaning the prices of existing cards will be affected too.

Fact 1: Majority of land will lay vacant.

Yes, I am sure. There will be very few who will be able to fill their land, let alone with what kinds of cards optimize it. It will be interesting to see for example, whether it is better to use 2 plots with gold level cards or 1 plot with max.

Players will have to weigh, which is more profitable, staking card on land or playing them.

This is as it should be - there should be the tension and inability to be able to do both (all) things simultaneously.