This is what he said a couple days ago.
I would have no choice but to take it up, McConnell said in a CNBC interview. How long you are on it is a different matter, but I would have no choice but to take it up based on a Senate rule on impeachment.
Senate rules say they have to "take it up". However, it's very vague as to what happens to initiate a trial. There is this one short part in there that says they discuss it. It's possible I suppose they could dismiss it outright and not take it to trial. But they have to accept the articles of impeachment from the congress.
https://www.govinfo.gov/content/pkg/SMAN-113/pdf/SMAN-113-pg223.pdfSide note. The rules also show an impeachment subpoena. In the form of a letter. Go figure.