I love the 2.5. But it is still a pushrod engine and cast block.
The biggest benefit of a 4 cylinder is weight. As mentioned there are other better lighter engines that use ohc cam(s) that can make 300hp better.
Heck I am playing with a 91 metro as a backup commuter to my 91 s10. That 1.0 complete longblock (without ac) 3 cylinder weighs in at 140lbs wet.
Guys have made 160 to 200hp reliably with stock heads, and the stock crank with high amounts of boost.
It is all about power to weight ratio.
There is a point where more horsepower requires more weight or custom expensive parts. I will take a 200hp 1800lb car over a 450hp 4000lb car any day of the week. Its not just the engine weight. You need bigger radiatior, stronger transmission, stronger rear end, bigger brakes, etc etc.
While it is great they are playing with the 2.5(if thats even what this is) sleeving a aluminum block and using a overhead cam could produce the same if not better streetable 50k reliable numbers.