Impeachment won't happen until / unless Democrats have a majority in the House of Representatives. That may or may not happen, but the earliest possible date would be in 2019.
If impeached, as noted, it would take 67 senators to vote to remove him from office.
By 2019, the Democrats might - might - have a slim majority in the Senate.
So there would need to be 15, 17, or more Republican senators who would agree that he should be removed from office.
By 2019, depending on how the 2018 midterm elections go, it is conceivable (to me anyway) that that many Republican senators would view Trump as enough of a drag on the party to oust him.
There are any of a dozen reasons he is eligible to be impeached & removed right now - it will be a minor point to elect one or two out of the many possibilities to use.
Impeachment and removal from office is a process that is about 90% political and 10% criminal / legal.