Sam and David,
My statement about getting it now really has nothing to do with the 2020 Mandate. Purely about being able to see the Full Traffic picture. If you are only using a "Receiver" you really need to be careful, as you are not seeing all the Mode C, S, 978 and 1090 traffic. Only pieces of the puzzle and that can lead to a false sense of awareness.
David, I agree, many will not ever need to have ADS-B Out, unless you plan on flying into Mode C areas after 2020. There is definitely hype about the install issue and demand. I don't buy it. However the market is very competitive now and that has driven prices down.. It’s just economics 101. This will remain the case over the next few years. But many and I predict the surplus of manufacturers will be weeded out and once that happen, I can assure you the prices will climb again. Once 2020 and the rush to install is over, the desire to be in the ADS-B market will soften. This is a very small industry in the GA, Private Pilot world and I just don't see it supporting more than a couple major makers.
The comment about Mode C transition speaks to the ADS-B side. I still use Mode C. The thing is ADS-B is ADS-B, it's not going to change. It receives 978mhz or 1090mhz. That freq wont change, but the FAA may add data to is. Thus you'd still be able to receive it. IE, that same FM Stereo you had 30 years ago still receives the same stations, only the content on the station has changed... was big band, now sadly maybe its pop.
My two cents... If I was selling my Plane, there are two ways to look at it. Get an affordable ADS-B In/Out so it is more marketable to a buyer, or don't and save the money to discount the price. The Aircraft market is soft right now, so if I really wanted to sell mine, I'd increase the curb appeal and ADS-B is a curb appeal at this time. Plus, I'd be able to benefit from the increased safety of ADS--B between now and then.
I hope this helps. You guys have a great weekend.