The short answer: It depends.
The follow up...
Every manufacturer which is using an umbilical between their controller and keypads is free to design it however they wish. Crestron, for example uses only 4 wires - 24 volts, ground, and Y & Z communications. They are wired into a phoenix type connector. I double up pairs of CAT-5 to use in this setup. (or more often, I run 4 conductor wire)
For stuff that uses CAT-5, the pinouts may be different from product to product.
What do you do? Well, I would just leave the ends of the CAT-5 sitting behind the wall unterminated until you get the product or know exactly what you want to get. Then, download the product manual, or call the company, and find out how it is wired.
You may be told that it should be done with standard ethernet terminations on the ends of the wire. Pinouts to do this are available all over the place online via Google. I don't make many ethernet cables, so everytime I do, I Google the pinouts.
If you want to wire a wall plate ahead of time, I would use one of the 'standard' ethernet pinouts and then make a jumper between the wall plate and the control system when you need to.