The HP2 is definitely the sleeper. I have owned many, many other Uniden scanners and have rid myself of all of them due to poor quality, bad firmware, poor performance. The HP1 and HP2 work like champs. Easy to use and rock solid. It just works... no fiddleing around with settings, it is truly plug-and-play.
I wouldn't hold my breath for an HP3. Unident doesn't even have an HP2 website. Only the old HP1. It should support other digital formats, so a firmware upgrade could open it up. But Uniden has to see th business case for it first. As difficult as it is for our hobby to swallow, it is on a path of elimination. As departments and agencies slowly move to LTE and other variations and encryption, it will lock us out. This certainly isn't in the near future but scanner manufacturers have to take this into consideration when millions of r&d dollars are at stake. They arent going to invest in new stuff unless they see a solid return of investment.
But back on topic, the HP2 in my opinion is the best scanner out there. Not to discount the Whistler as I love them too. If you do buy an HP2, you won't be disappointed.