All around solid device. Great for Plex streams and basic gaming.
I'm 4+ years into two shields, no desire to upgrade. You'll be fine.
The 2 new devices don’t even have release dates and most likely will be a very minimal upgrade over the existing models
The Shield is still the best android TV device out there, if not the best set top box in general. You’re fine.
It might be a bad idea this close to the launch
Can you return it?
If the new device supports Dolby vision and hdmi 2.1, I say it is a lot more attractive than the old device. If you care about those things.
I still have my 2015 model and couldn't be happier, I prefer it over the 2017 model
I have the 2017 flash version and can say that it's gotten a bit slower with the last major Android update, so i don't know how many it will still get.
But it's outperforms every other media player available at this time.
If you can wait, i would buy a cheaper device in the meantime, if and when there will be a new version is currently unknown.
All we know is that there is in fact a new revision of the Nvidia Tegra X1 ARM CPU, which is now used in the new Switch the revision and brings at least lower power usage, it's not unlikely that it also packs many new features aswell.
They are still supporting the 2015 Shield models, so I think you're fine.