I thought six years was a good time to analyze whether SP had any impact. From a humble perspective I wanted to analyze this for my world, not for the whole world, as I do not have the TLM statistics readily available for the whole Catholic world. I define "my world" as all the cities I have lived in so far. These are 1) in Switzerland: Zurich, Luzern, Basel and Bottmingen 2) in Germany: Munich 3) in the United Kingdom: London and finally, 4) in my home country Austria: Linz and Vienna.
Additionally I thought it makes more sense to look for regular TLMs on Sundays and Holy Days of Obligation as well as at the establishment of personal parishes. So I did not consider the odd mass on one Thursday per month or something similar, because these irregular masses do not lead to a build up of a stable group of faithful. Also, I did not consider TLMs celebrated by the Priestly Fraternity of St. Pius X. (FSSPX), because the FSSPX, while being part of the Catholic Church, is canonically irregular and hence not impacted by either "Eclessia Dei" or SP.
Let us start with the analysis in Switzerland, in the city of Zürich. Before and after SP there is a Sunday TLM in Zürich-Oerlikon (Herz Jesu Church), run by the Priestly Fraternity of St. Peter (FSSP). No change. Apparently this TLMs is now associated with a personal parish "St. Maximilian Kolbe", which is beautiful
but in terms of the Mass itself, no change. And this Sunday TLM is still at 5 pm. So no change. Lets move to Luzern. There the Sunday TLM is in the "Sentikirche" at 9:50 am, and this has not changed since SP. In Basel, there is a Sunday TLM with the FSSP at 10:30 in St. Anton church run by the FSSP and one in St. Joseph church at 5 pm celebrated by the Institute of Christ the King (ICRSS). Both have not changed since SP. Bottmingen lies in the canton Basel Land. In the whole canton Basel Land there is not a single Sunday TLM. This is also unchanged since the TLM.
In Munich there is one Sunday TLM in the St. Anna church (Damenstift) at 8:45 am and this has not changed since SP. In London there is of course the BromptonOratory where there is a Sunday TLM at 9 am and in St. James Church (Spanish Place) at 9:30 am. Both churches are not personal parishes for the TLM and offer also the novus ordo mass. In large cities like Munich or London one would have thought that at least there, the TLM personal parish as foreseen in SP by Pope Benedict XVI, would be implemented. But this is affirmatively not the case. Certainly the TLM in the Brompton Oratory was there before. Perhaps the TLM
in the St. James church is new. So maybe a small change in London, but I am not sure.
Finally, Austria. In Linz, there is as there always was, a TLM in the Minoriten church. This TLM actually was there all the time since the novus ordo was introduced by Pope Paul VI. in 1969 since the local priest simply refused to celebrate the novus ordo. Later this mass was taken over by the FSSP. There are even two TLMs every Sunday morning. A low mass at 8:30 am and a sung high mass at 10:30 am. In Vienna the FSSP are also strong and they offer the 6 pm mass in the Capuchine Church above the Imperial crypt since many years . It seems however that they now also offer a Sunday morning mass in the Church of St. Peter and Paul (3rd district). I believe this TLM to be new and perhaps due to SP. However it is a long time since I lived in Vienna so I cannot say for sure.
So in conclusion I have to say, at least in my world, summorum pontificum had no impact. This is a sad thing to say on the sixth anniversary of this important document, but it is the truth.
What could be the reason? One reason is certainly that the traditional faithful are not united. The Ecclesia Dei groups such as ICRSS and FSSP are not united in some cities like Basel there are even two small TLMs competing with each other instead of uniting into one personal parish. And in addition the Ecclesia Dei groups are fighting with the FSSPX, the largest traditional group in terms of priests.
Another reason is, although Pope Benedict XVI. wanted the change, 90% of the bishops do not want to see an increase in the traditional mass. Already before the very unfortunate resignation of Pope Benedict, the talks of the FSSPX and the Vatican had ground to halt due to the appointment of Bishop Müller of Regensburg, an arch-enemy of the traditional mass, to the position of head of the congregation for the doctrine of the faith. The CDF is also responsible for the papal commission "Ecclesia Dei" and the talks with the FSSPX. Of course there will be no further impact of SP in the pontificate of Francis, as Francis, when he was archbishop of Buenos Aires, did actually prevent the implementation of SP.
There are difficult times ahead.
Let us hope and pray for the Traditional Latin Mass.