I would say no. The 27" retina is still fairly new and I think a great time to get one.
I just ordered a refurb of the 4GHz/M295X which is a sweet spot in terms of price and performance and better than the low-end Mac Pro in some cases.
If you find it is underperforming for what you need, you have 14 days to return it and get a higher-end Mac Pro.
I ordered the 4 32 M295X 3TB from the refurb store. I've noticed they go quickly when they show up.