Applicants for a U.S. green card (lawful permanent residence) based on marriage sometimes ask, “Can I avoid the Visa Preference System and long waiting period by simply waiting for my spouse to become a U.S. citizen?” They know that, as the spouse of a lawful permanent resident, in category 2A, they are likely to wait a few years for a visa number, and therefore a green card, to become available to them.
However, you don’t really gain anything by waiting for the petitioning spouse to become a U.S. citizen. In fact, you could actually lose time if your spouse’s citizenship gets delayed.
Let's start at the beginning of the process and see how it plays out. No matter what, your spouse will have to submit the visa petition (USCIS Form I-130) sometime, even after he or she becomes a U.S. citizen. The form to use is the same, no matter your spouse’s status. And after U.S. Citizenship and Immigration Services (USCIS) approves the I-130, your approval notice will remain good even after your spouse becomes a citizen. In other words, your spouse could file the I-130 now and put you on the waiting list -- but if he or she becomes a citizen while you're waiting for your Priority Date to become current, you would automatically become an immediate relative, and could file the rest of your green card paperwork right away.
If you're lucky, or if your spouse's citizenship gets delayed, your Priority Date might become current before he or she becomes a citizen. In that case, you would definitely be happy that your spouse had filed the Form I-130 without waiting.
Another consideration is that the longer you wait, the higher the I-130 application fee is likely to go. (One of many fee hikes was scheduled for December of 2016.)