A couple of notes from my perspective -
There will not be a scanner out there that decodes digitally encrypted signaling. I think we've beaten that issue to death in other posts, but I'm comfortable saying so. There are two terms for someone with a radio that has the proper crypto key: "on the job" or "under arrest."
Technology changes much faster today. Eleven years ago we had divergent digital formats. Astro for Motorola, Aegis for Ericsson/ GE. Then P25 was developed to address the divergent formats with a common protocol. Problem was that the manufacturers dragged their feet through the process and the ISSI segment of the standard was only finalized a short while ago under federal threat to finish business or they (what was the FLEWUG) would make something up and the manufacturers would need to adopt it to be eligible for federal procurement. I've said it before - there are people who have sent their children through college working on P25 and it's still not done. Unfortunately it has lost its relevance to two important issues (these are very convoluted; I'm only putting these in very basic terms):
1 - The FCC has mandated 1 voicepath in a 6.25 kHz channelspace. P25 phase 1 cannot do this and the phase 2 solution will likely have to be TDMA to accommodate 4 simultaneous conversations in a 25 kHz channelspace. This means that P25 phase 2 will look something like OpenSky or Tetra. Is this bad? No. In fact, scanner manufacturers are part of the P25 community. Can it result in a new generation of scanners? Probably. The manufacturers may do a scanner as a proof of concept for their land mobile product lines. Will scanners ever recoup product development costs? Hell no! This is a niche market. The only bigger loss per R&D dollar are fire/ EMS alert pagers.
2 - Scenario 2 is dire and will kill the hobby. There is a movement that began independently - first, with Cyren Call, then with some other entities, where they explored 700 MHz. Morgan O'Brien, the founder of Cyren Call wanted to capitalize on the 'homeland security' monies and federal grants to do away with the auction of 700 MHz to commercial interests and give it to public safety. Well, on paper, anyway. What he really wanted to do is make another cellular company on the backs of public safety. The rationale is this: you have a road that everyone uses. You don't build special roads for public safety vehicles. Public safety vehicles have lights and sirens, so they can get the right of way if there is an emergency. Same thing with Cyren Call's system. The public would be on it (giving ol' Morgan more revenue than public safety ever would), but the system would prioritize public safety higher and give responder access percedent. And, if you wanted a grant, you would have to buy the official grant radio. How could this fail?!
Well, Congress already spent the money that the Commission was supposed to raise from this auction, so they could not stop it. Alas, it's doubtful that all of the former Commission attorneys and engineers that O'Brien hired are going to fish Cyren Call out of the toilet. Some may recognize Mr. O'Brien's name as the founder of Nextel who was successful in transmogrifying the specialized mobile radio sysems of the 80's and 90's into another cellular telephone company (and caused very poor decision-making on the FCC's part by allowing cellular-like digital immediately adjacent to public safety radio channels).
There is more. The data channels on 700 MHz allowed "wideband" or 150 kHz wide data. Some people in both public safety and industry said, "why waste time doing that when we can go straight to broadband within that channelspace?" The capitol region was the pilot project, and it worked. Now, the movement is for a "national licensee" to get the license for this portion of the band and administer access by public safety agencies (and possibly the general public on a secondary basis). Software defined radio makes it possible to have the device roam around on various bands and protocols.
What some say will happen in the next five years (nevermind 15 - 20 years) is that public safety radios will be computers with RF modules on 700 MHz. The radio part will be an application that behaves like a radio and the RF part will actually be running on broadband with IP addresses and not distinct frequencies. This means that encryption can be done very cheaply at the application layer and - even if there were a bright few who knew enough to sample the data stream - chances are good that everything would be encrypted. Even if not, the bit stream will be to a unique IP device, which may or may not be where you are. The only way to work through this is for agencies that value their public interaction to webcast non-sensitive traffic. Essentially this mode will work like a webcast on the most basic terms.
The very latest has been Google's proposal to the FCC that spectrum should be auctioned on a real-time basis. This means that public safety slots may be the subject of ad-hoc auction which may limit availability. The ramifications of his need to be explored in greater depth.
The crystal ball is hazy, but there is one thing that is sure: These are the times the Chinese speak of in their curse: "May you live in interesting times." Things are going to change very fast. And some things will not change at all. There will still be volunteer fire departments on 33 and 46 MHz. Just like eveyone said that by the year 2000 we'd all be driving jet cars and living in Jetsons houses. That hasn't happened, yet the world is much different than it had been.
All I know is that I would be perfectly happy if my 1978 vintage Regency SP-H/L scanner worked for my application. But it doesn't and has taken its place in the curio.