I suppose the spiritual successor to the 131 Sport was the Sporty Strada/Ritmo cars. The Sport went out of production before the introduction of series 3 131s so the series 3 Supers were the successors of the series 2 Supers.

Now whether the Strada/Ritmo 125/130 were apt successors to the 131 Sport is a different question. I find it hard to compare a front wheel drive hatchback with a rear wheel drive saloon/coupe. The driving characteristics of the two different types of car are so different that makes direct comparison difficult. But we are talking of spiritual successors and in spirit the cars are similar so the answer has to be 'Yes'. But I also think that you can't claim the Ritmo/Strada 125 is the successor but the 130 or even the 105 isn't. 

Personally I prefer the look of the series 2 Strada and I think the Abarth 130 really looks the business! I've driven Abarth 130s and they are fabulous cars  Haven't driven a 125 or a 105 but I suspect they are similar in character to the 130 albeit a little 'softer'.