I wouldn't say your hobby is coming to an end. It certainly will become more challenging though.
The same happened in Clarksville / Montgomery County about 5 years ago. More recently, every county in Northwest Middle Tennessee has switched or will be switching to LTR Passport trunking as well. It'll be interesting to see how Hopkinsville / Christian County makes the switch. The recently posted update in the database regarding Christian County's new system says that the original plans for an MPT-1327 system have been scrapped and indicates that Hopkinsville / Christian County is leaning toward a more mutual aid-friendly system. This is certainly great planning, if it is indeed the case. The ability to communicate with other agencies is essential in large scale disasters.
Interestingly, Palco Communications maintains Christian County's VHF system. Greer Communications has been largely responsible for the build-out of the Tennessee Homeland Security District 7 system. I suppose that doesn't necessarily mean that Greer will be contracted to do the same for Christian County, however. But, unlike Greer, Palco is a Motorola dealer. I'm unsure what implications, if any, that will have on the design and construction of this system.
Perhaps an LTR Passport-capable scanner will become available soon. It wasn't too long ago that folks in Nashville had thought their scanner-monitoring days were over when Nashville switched from VHF to an 800 MHz Motorola digital radio system. However, soon after the switch, Uniden released the BC250D digital-capable scanner. The likelihood of Uniden or the other scanner manufacturing companies releasing an LTR Passport-capable scanner are slim, at least in the near future. But, in the mean time there are tricks that will allow you to monitor the new system. I'd recommend searching for some of the older posts and threads on the Tennessee Homeland Security District 7 radio system and scanner monitoring in Montgomery County, TN. Some of those post go into quite a bit of detail as to how to go about monitoring the system.
In short--the way the passport system works is that each user (whether fire, sheriff, or PD) will access the "home frequency" first. However, if that frequency is busy, their radio traffic will be shifted to an alternate frequency. Usually, the best practice for monitoring Passport is to listen to the home frequency. You'll hear a variety of radio traffic and unfortunately won't be able to separate agencies.
To know what you'll likely be up against, you could give it a try by monitoring Montgomery County's system. You should be able to monitor it from your location, although the signal may be weak. 453.3375 MHz is the home frequency for Montgomery County's system.
As the switch-over date nears for Hopkinsville / Christian County, jump on these forums. We can give you more information on monitoring and some of the tricks we've learned in our attempts to monitor the Tennessee system.