So I would like to use Retopoflow for Blender 2.8 but it requires an update by the looks of it, so I searched around for a solution but no luck. Any idea on how to update it? Thanks for your time.
I would have preferred to post this as a comment but I need to have 50 reputation to do that.
As has been stated, the authors have stated that a 2.80 version will be produced and that work would begin once the API had stabilised. I would assume from that the at least initial work has therefore begun as the API was declared as stable when the public beta launched.
The point I wanted to contribute however was a tip on working between versions. I have found a number of issues with the import/export addons, which again translate back to the current beta status and the fact that most import/export is considered as an addon to the core functionality and thus lower priority.
What has worked really well for me so far is (surprisingly) copy/paste. It will no doubt depend a lot on the structure of your objects but in my case I have been able to select the objects I need to retopo while in 2.8, ctrl-C to copy them, then tab over to Blender 2.79b and paste them in (ctrl-V). Occasionally I find the copy/paste buffer is not picked up, but reselecting and repeating fixes that so I suspect human frailty more than bugs, is responsible for that.
I hope this helps. Perhaps a Mod might copy this up to a comment on Craig's response as it's not really adding anything new to his answer but simply offering some further hints for Craig's suggested workflow.