It can happen. The length of speeches over time has been on a downward trend. There used to be no limit on the time members could speak. Then it went to, I think, 40 minutes—no, even longer than that initially, and then down to 40 minutes, and then down to 20 minutes, and then it was splittable, and so on. Again, it's entirely up to the committee to decide what is an appropriate length of time for a speech.
The only thing I would say is if you go too low, then you put at risk questions and comments. Let's say you said the maximum speech length would be five minutes. Well then, how long are questions and comments going to be? That's a problem.
The other thing I would say is I'd probably disabuse you of the illusion that reducing the length of speeches will reduce the number of members who actually get up to speak. With 338 members, more members will come forward to fill that time. That's what will happen.