Are there other "estates" that the framers of the constitution neglected or did not know about that should be in the US Constitution?

I was a bit confused by the use of your term "estate" until I recalled French History where the parliament prior to 1789 had been set up to represent different groups of people, each possessing their own estate, and that a successful law had to win approval in all three estates.
The US essentially has two legislatures: the Senate and the House of Representatives.
Each state is represented equally in the Senate regardless of its population. So you wind up with Wyoming having as many Senators as California, Texas having as many Senators as Vermont. This isn't a democratic set up, but it wasn't intended to be. Under the Constitution, each state retains some sovereign powers. To protect those rights, a Senate was established. There are currently 100 Senators, 2 per state. Should another state be added to the Union, there would be another two senators added.
The House of Representatives is a different matter. There the number of representatives in each state is based upon its population. A census is taken every ten years to adjust the size of each state's delegation. So if a state loses population or gains population by a smaller percentage than the other states, the size of its congressional delegation will shrink. Currently, there are 435 Representatives. Congress can vote to increase or reduce that number.
For a law to be enacted, it must win approval in both the Senate and the House of Representatives. In addition, each chamber has unique responsibilities. Tax bills must originate in the House. A bill of impeachment must pass the House. The Senate alone has the power to ratify treaties, confirm Presidential appointments to the Cabinet, to the judiciary, to independent agencies, as well as top military officials. The Senate follows up on the House impeachment bill by acting as a jury and determining whether the impeached official should be removed from office.
There doesn't seem to be any sense in creating an additional "estate" or division within the legislative branch. It's difficult enough to get something through both houses of Congress today. It's not clear what unique powers an additional "estate" would have. Besides, it's not clear what a third estate or division within Congress would represent.

If a prison was in the path of a wild fire, what would take priority, getting the prisoners out or making sure they don't escape?

Although prisoner lives may be high priority, prisons are not evacuated when the fire alarm goes off. If they were any prisoner with a match could go free.

Phase 1 is to find out where the fire is and seal off the rest of the site, while calling emergency services. Then people are evacuated from the fire zone to another part of the site. Although this isn’t regularly tested, the guards are trained in what to do.

If a building (or more) became uninhabitable, vehicles would be ordered to transport the prisoners to other facilities. So, at no point would the prisoners be standing around, outside the prison.