I think the hype/overpriced situation of 1&2 wont last long.
I really do want to support the kickstarter but with just digital, I dont feel I would "gain" anything from my money other than something I have to eventually delete off my PS4.
I think more importantly you are supporting something that many thought would never happen, and a game that is being handled by one of the most innovative game developers (Yu Suzuki) of all time.
I am not one for digital either, in fact I avoid it unless it is completely free. However, supporting this game, no matter what the platform or means of distribution means more to me than anything else. I am proud to be supporting a game I've wanted more than any other for 13-years, and I think it's so cool my name will be in the credits for supporting its development. That is definitely something I could have never imagined at any point while I was paining over the real possibility that this game would never be made.
So in a way supporting Shenmue 3 and the Kickstarter is a gesture of supporting something you are passionate about more than whether it will be delivered digitally or physically, at least that is how I feel.
There is speculation that if this Kickstarter is successful enough, Sony may offer a physical release at a later date and time, possibly even as part of the Kickstarter. But this is speculation and rumor at best at this point.