You’d be losing out on the deal.
There’s been almost no increase in performance from Intel in the last few years, so going from an i7 to an i5 will be a downgrade. The only tasks that would see a benefit would be tasks that are purely single threaded, and that’s only if the i5 is overclocked.
For gaming you’d see zero benefit from the trade. For productivity you’d see a decrease in performance from the trade.
And the switch to DDR4 will also have zero performance increase as well. DDR3 and DDR4 performance in just about any task outside of synthetic benchmarks is completely negligible. Hell, I’ve seen plenty of DDR3 performing better in synthetics compared to DDR4.