And if they vote no?

More impeachment law:

House Democrats will discuss on Tuesday morning how to move forward, Pelosi said on Sunday, with the chamber possibly voting to send the charges to the Senate later that day.

OK, for all you weirdly named TV lawyers, I got one for you.

Can the House reverse its own impeachment proceedings after already voting for them? 

There is no empty space between impeachment and trial, except a variable delay slowness of motion.  That is the direct reading of the Document.

Nancy and Mitch are doing some sort of weird dance, and its all mixed up in the election schedule. What if Trump filed to just get on with the mess, claimed the House cannot reverse and the delay is an unconstitutional act.  Roberts and his buddies are dim bulbs, but they will be perplexed, Trump is right, he can demand the mess proceed, there are no actions needed between part one and part two.