I've always felt that Sentry makes some of the most reliable, well built mechanical sirens on the market. They keep it simple, while still offering impressive outputs. It seems like they definitely have mastered the concept that if it ain't broke, then don't fix it. We see this from the M-10 still in production today as the 10V series, and until a few years ago, even the impressively low pitched 5V.
In the last 10 years we've seen several new models come to the market, and it seems all have been quite successful (less the Defender, though I think even that was a good product with solid engineering.) This begs the question though; are the 13

These are my thoughts on that subject:
The 3V8 is great. It fills a niche in the market that really no other manufacturer (mechanical) can really fill. The Model two is really the closest thing I can think of, and even that is essentially 2 times quieter. Perhaps the skirted option doesn't make a lot of sense for most communities, but I think it has a very important place in an industrial setting. I'd keep that one for sure. The added battery function will do very well too, as many tiny towns can faithfully rely on these for warning and VFD needs.
Moving on to the 7V8(/B) series. This is definitely a killer siren, and an excellent add to the lineup. But it very much is taking away from the standard 10V. Is the 10V really that necessary anymore? The 7V8 is slightly quieter, and the -B is twice as loud. I hate to think of a world without them, but I just don't see the economic value of continued production.
Now the 10V2T, on the other hand, is just awesome. It's loud and has a very distinct tone, but it again is eclipsed by the 7V8-B. I'd be very interested in seeing this siren live on, though. It's somewhat popular, and I think does serve a market somewhat.
Unfortunately I don't see a reason for the 15 and 20 anymore, though. They are big, loud, and not nearly as efficient as the battery powered 16V1T, and new 14V. I'm actually surprised that both models are really produced at all anymore. They have pretty demanding power requirements, and you just don't see many new installs to a significant extent.
The 14V and 16V are just monsters. I think they are definitely a great place for Sentry to be right now, and I am sure the battery features of each will make them popular choices for many years to come.
Lastly is the 40V2T series. Might it be time to see the AC version make a very sad departure. Is the extra 800-1000 feet of coverage over the 16V worth the production costs? I haven't seen the 40V2T-B specs yet, but I imagine that true to any -B variant, it is at least 2dB louder than the AC-only, which would give it a large advantage over the 14 and 16 series sirens. I imagine this siren isn't going anywhere anytime soon.
This definitely isn't a jab at Sentry, more just some things to think about. I welcome input from users here, and I would definitely like to hear some insight from Sentry or Ed Wise about what the future may hold as far as consolidation of the product line.