I'll answer that question for you.
The bill will come to the floor when scheduled, at that time, each Senator who request a floor time will get it.
Unlike the House, there are no time limits on the Senate so each Senator can hold the floor as long as they want.
Before each Senator who has requested floor time has yeilded the floor, the only way to stop the debate is by a vote of cloture, which currently requires 60 votes.
Even if a vote of cloture is not possible, the Republicans can go ahead and start the debate process by scheduling the vote.
If each member who requests time on the floor has yielded the floor at least once, then a simple majority of 51 could end debate and the vote would be taken.
If the Republicans do this, the Democrats would be forced to "Filibuster" by continuing to speak and thus not yield the floor.
If all the Democrats refuse to take the floor, then the vote would be held. This is what "forces" them to talk, the fact that the vote will come up as soon as they stop talking.