Not quite correct, current command upgrades include anything from K-area FO's willing to move to a Euro base for a command, to people who joined in the last big recruitment drive in May 2014, who were then laid off for the winter.
Yes, it is correct that if you joined now you would be at the bottom of the Master Seniority List and most likely be in for a long wait before getting your base of choice, and in the meantime quite possibly moved around the network a fair bit. Whether or not any layoffs will happen this year is anyone's guess, given the current pilot shortage.
Given the strict enforcement of the Master Seniority List though, unless you meet the requirements for command on joining, you'll be in for a long wait. If you have the required hours for command, 2 consecutive sims graded good or better are required and then you need to pass a quite tough command assessment, realistically expect 2 years. Oh yes, should anyone above you in the seniority list meet the minimum requirements in the meantime, you're out until there's a space for you given your seniority. The only reason people who joined recently are getting upgraded now is because they met all the requirements on joining.