I'm trying to figure out what direction I need to go. Now that the Yun is dead I'm not left with many choices. Of course the Raspberry Pi is available and I'm looking at going that direction, but, it's a little frustrating that it uses 3.3V I/O verses 5V. A lot more 5V sensors around than 3.3V. Also no built in analog I/O. Also power hungry (runs hot) 2.5A power required. Just to use my standard 1-Wire DS2482-100 board I need a level shifter for the I2C connection. Edison and some of the other similar products have other issues and don't have a large following. I was using the Dragino Yun Shield but it is getting hard to find also.
What was nice about the Yun is that I could track data on a flash card using RRD. I made a board that has 4 of the DS2482-100 chips (which is the maximum given the address settings). This was 4 separate channels that could easily handle 20 temperature sensors on each channel. Currently we use one of these setups to track beehive temperatures in the winter to get an idea of which hives have died. Not unusual to track 40+ hives. Also use the same setup to track geothermal system and other H&V equipment.
Now if I ever want to build another of these units I need to figure out something else to use.
What is new that is coming down the line or am I stuck going down the PI direction? Any other ideas?
I'm not at all clear from your description what features of the Yun you have been using. If the key item is an SD Card then you can get an adapter for any of the Arduinos.
Is the Yun Shield (that can be attached to an Uno) still being made? - I don't recall who made / makes it.
Have you the option to have a centralised WiFi connected server (perhaps on an RPi) and use an Uno (or Nano) in conjunction with an ESP8266 WiFi module for operating your sensors and sending the data to the server, I mention Uno + ESP8266 so that you have the advantage of a 5v MCU.
The ESP8266 is a 3.3v device but if you can live with that then maybe something like WemosD1 or the NodeMCU would be suitable.
And there are other wireless options if you don't want to use WiFi.
It wasn't just the SD card, it was the ability to do higher level programming such as using RRDtool and the round robin database to track data. Also setup a htm page on the Yun and plot the data graphs. Unless your going to go to a dedicated remote server to do the data logging, the ESP8266 is not going to help.
Actually didn't even know they had come out with the REV 2, thanks, starting looking into it. Hopefully it doesn't die off like the Tian did (tried one but it never had the software support to get it working, such as the bridge). At least the Rev 2 appears to be the same with just some improvements that I wish they would have had in the original.