The best way to get in a say so for SCS to take notice, is to have a specific state poll. Only states that are adjacent to existing states are part of this poll for next in line. No need to really leave feed back unless you just want to explain your state of choice with an explanation. Let the voting began.
My vote goes to Utah. To start the process of boxing off the map with hopes of Colorado to follow.
Edit: Feb 1st, 2018
With Oregon officially announced as the next dlc state, the selections have been reset for the next selection for 2019. I will manage the polls and keep it updated once new map dlc is announced moving forward. With the new poll selections, I only say 2019 until it is official that ATS has parallel teams working simultaneously. So 2019 is added to each state instead of 2018 because we may not get 2 map releases this year. The attached pic is the poll result for the 2017 voting as the next state.

Edit: Jan 26, 2019
With Washington officially announced as (1) of the next dlc state's, it is now removed. The 2nd state was not revealed in the ATS 3rd anniversary stream as expected. Based on the teasers from 2018 and the subtle hint from Pavel in the anniversary stream, I will assume that state is still Utah. So, Utah is also removed and the polls are reopened for voting. The attached pic is the poll results for the 2019 voting.

Edit: Dec 20, 2019
Well, it's time to reset the polls everyone. Thanks for another year of contributing. Another year of great talk. Looks like our front runner Idaho is a reality now. Many of us wanted it so that the gap between Washington and Oregon can link up Utah and New Mexico dlcs to avoid majority of the base map if they choose. The announcement of Idaho came Dec 19th on the Xmas stream this year. Awesome that SCS flat out reveal what's next instead of hinting. We now have 100% confirmation of the next state that will join our beloved ATS in 2020. The other state isn't known yet but based on Pavel's comment on the stream, SCS isn't ready for Texas yet and I agree and applaud that. So no Texas for 2020 for sure. The hopes of boxing up the map in the West is still a strong desire for many fans I have come across. Idaho gets us another step closer to that box. With that said and the recent findings in the game files for both Idaho and Colorado, the second state based on context clues is assumed to be Colorado. So in order to reset the polls, I must use this assumption and eliminate Colorado as well for voting even though it was not revealed. With Texas ruled out, there are only so many directions SCS can go that makes sense. Apologies to anyone who doesn't agree or is not convinced on Idaho and Colorado for 2020. Remember, this poll/thread is just for speculation and fun talks about states to come.
The year end results for voting in 2019 for the states to come 2020 is below

Edit: Nov 28, 2020
Time to reset the polls again. Its not 100% confirmed yet but based on this blog, its a pretty easy teaser to indicate the next state. If we all are incorrect, I'll just have to reset the polls again to make it accurate. But moving forward, I will only remove one state at a time because SCS is not revealing both states at the same time as once thought. So you guys will need to reselect after each state is more or less confirmed or hinted. South Dakota replaces Wyoming now. Although not likely a 2021 map, it will be included as a 2022 selection but still selectable. So since one state has been teased for 2021, the selection goes to only one remaining state that can come for 2021. So 2 options are removed for now. Once the 2nd state is confirmed for 2021, the poll will return to (2) options for 2022.
Here is the poll result as it stands for 2021 before the reset

edit: Dec 21, 2020
Well, Texas just got confirmed so I rest the polls for all of 2022 now.