1) This is just the initial Republican proposal. It stands virtually no chance of being passed as-is, since it requires the support of Democrats in the Senate who tend to be pro-immigration. Democrats will likely be the adults in the room and push back heavily on it. They may decide to kill it completely, since Republicans cannot even attempt to jam this through Congress the same way they tried with healthcare.
2) Even once passed by Congress, it would take several years for the final legislation to be fully enacted. Existing applications are unlikely to be affected.
3) The most likely outcome is that, like healthcare, nothing changes because Republicans aren't able to get it through the Senate.