This was a stupid move by Pelosi, so it figures that it was based on advice from Lawrence Tribe. There is absolutely zero chance that McConnell caves on this. It would amount to letting the House have a veto over the Senate's rules of impeachment, and he won't ever let that happen. So, he's got two options:
1) Deem the articles transmitted by virtue of the vote being held, certified, and publicized, and move ahead with the trial anyway, or;
2) Announce that the House has just wasted a whole lot of taxpayer time and money to try to remove a duly elected President, and now are refusing to send over the articles. If the House isn't going to send over the articles, then he's not going to waste the Senate's time debating rules for a trial that may never happen. So unless and until the House sends over the articles of impeachment, the Senate is going to move on to other matters, and considers the impeachment over. If the House ever does decide to send over the articles, then the Senate will begin discussing the rules it will use for the trial.
I prefer 2), simply because it puts Pelosi back on the hot seat. The Democrats will look like idiots if they've gone to all the trouble of impeachment, but then refuse to send it to the Senate for trial. She'll have to cave after getting nothing in return.