I am going by what KD has done in the past with major "build from scratch" coasters. The park tries its best to have the new coaster operational by opening day. There might be some exceptions like Twisted Timbers where most of the existing footprint/footers were kept "as is". (Though, I would not be surprised if some existing footers had to be recast or reinforced; there could have been new footers added due to the new elements introduced to the ride during the RMC conversion).
From KD's perspective, even Dominator was a "build from Scratch" coaster. Instead of the ride structure coming from the factory, the ride was brought from Geauga Lake park (some pieces of the track were sent back to the factory to be re-worked per recommendations from B&M). The land prep for the ride started in the summer.
We just have different definitions of what "land Prep" means when it comes to a coaster being built. Pushing dirt around with a grader/bulldozer is only part of the land prep. Core samples taken; surveying done and markers put down for the layout; footers dug out; custom concrete forms and associated rebar built; concrete poured; concrete cured. When that is done is when I consider the "Land Prepped" for the installation of the ride structure. (Keep in mind that the footers being built may be staggered due to the order in which the coaster is constructed and the needed access of heavy equipment to those areas).
KD's GM Tony stated in the ACE 2019 Fall Q&A session that any new coaster coming in the future will need to have good capacity and reliability. He pointed to Dominator as the example. So, *IF* a new coaster is going into the Volcano site, then it would need a minimum throughput of 1000 folks per hour (I thought most B&M's can handle 1200 folks per hour) and be reliable. So, I don't see a RMC compact single rail coaster being installed like the one at CGA and at a couple of the SF parks. (Unless, KD makes the coaster a part of a larger expansion with other new attractions added). But, Tony seemed to place a big emphasis on capacity with the next new coaster. I thought the raptor capacity was 700-800 folks per hour.