Something tells me we won't be seeing any new features added to the P3 series. If it is a software update to allow it then maybe but they need features the older Phantoms don't have to drive the sales of the new craft. The P4 will start to see different versions such as the rumored P4 Pro. Also the P5 is just around the corner.
I suspect broad-based upgrades for the P3 series are going to be limited from here on out. Anyway, I think that tripod mode is more likely related to hardware rather than software. The Phantom 4 has two compasses and two IMUs.
Maybe (probably) not from DJI. We might see 3rd party developers implement a similar feature though. No reason why Autoflight logic for example couldn't easily do this with the custom flight controller, simply modify the user stick inputs before sending the commands to the AC.
Autopilot Cruise-mode is a very nice "tripod" that can be arbitrarily moved. Give that a shot!
I have flown over 300 flights of all kinds and I never used DJI Go for any of them. I use Litchi, Autopilot and FPV Camera. Anything DJI will implement in GO for Mavic is most likely available in third party apps for the P3P and P4.