I dont see performance increasing substantially. Most old school hatches will keep with or out perform modern equivalents. The cars now are less raw and more refined. The area that has improved is possibly safety. But even this is arguable point.
I think you have to remember what a hothatch is. It is a fast version of the normal hatchback equivalent. To be desiravble the original car really has to have some character too. I think the Renault 5, 205, phase 1 clios, etc are all good cars, IN THEIR OWN RIGHT. The original cars now lack character, and this spills over into boring hothatches that also have no soul. The modern cars all look the same. I think this is as a result of too many committees having input during the design stage.
Its a similar situation in formula one. Schumacher should be a real hero, but he isnt. He doesnt have the same kind of following as someone like Jean Alesi, who only won a single race during his career. The reason is that people love emotion. Schumacher shows no genuine emotion, whereas Jean cried, laughed, and in essance was human. I think the older cars have emotion like Alesi. The modern cars are just fast, efficient Schumachers.