You seem to take great joy in mentioning this every chance you get, but the overlapping of design & construction is irrelevant here. We are talking about "planning," ie the entire design phase, starting with blue sky. I mentioned construction only to emphasize just how long these projects can sometimes take to fully bring to fruition, and the one I chose to use as an example was not "fast tracked" by any reasonable definition of the term. It took more time to finish just the construction than entire parks. So have several other projects in recent years. So even if they decided they're going to build them the day before they were announced (or actually brought out the equipment unannounced in Universal's case), which they obviously don't do, it would not make any difference.
If they are going to replace Simpsons before the contract expires, and do so competently, they need a solid idea yesterday. They can't just start demo when the time comes and then fly by the seat of their pants (and I guarantee that's not what they're doing in LC.)