I appreciate you looking out but I've explored every option, based on price / performance balance the imac pro with some external SSDs are the best option for my purposes.
No more recommendations for a different setup please. This thread is just for speculation on the iMac Pro life cycle.
I think you should:
a) wait for Mac Pro revelation
b) ask other professionals in your field for other suggestions because I feel you are too locked on the iMac Pro and kinda blind sided. (don't mean it aggressively here) The reason I say this is because I understand this. When one does his/her research and then lock onto something its hard to even hear other (and sometimes much better) suggestions.
So my advice, wait for Mac Pro, take a step back and re-evaluate. My friend is classically trained composer doing orchestra etc. for all sorts of stuff (including feature movies - sorry, won't reveal this person's name) and this person worked before iMac Pro existed.
Just free your mind and try different approach. 'Lust' is an awful devil