The bipartisan "Gang of 7" negotiating in the House of Representatives have cooked up an immigration reform proposal that involves a tougher path to citizenship than the one envisioned in the bill that passed the Senate.
The way the House Gang's version works, is that instead of provisional legal status otherwise law-abiding unauthorized immigrants to the United States will get probationary status for five years. At the end of five years, then if the E-Verify system designed to make it hard for people to get jobs without work permits is "fully operational" the path to citizenship continues. But if it's not fully operational, the probationary status will be revoked. In political economy terms, that gives people enjoying probationary status good reason to lobby for E-Verify implementation. If probationary status isn't revoked then after 10 more years (in other words, 15 total years rather than 13 years as in the Senate) people would become eligible for citizenship.
Now the key to understanding this whole thing is exactly how do we decide whether or not E-Verify is operational. Is it President Rubio's call? Is there some objective criteria? Is there just going to be a huge political fight over it? In practical terms, though, the main issue House Republicans are going to have with this bill is that even though the differences with the Senate bill are meaningful the fundamental template is similar enough that if it passes you're bound to end up going to conference and House conservatives have developed a kind of paranoia about conference committees.