To become the dominant form of troop transport would be the best way to quantify it.
There was no surge in base captures by M3s when those changes you mentioned were made. The shift from bomber to vehicle base captures was a gradual and very slow one, starting back when Gv's were introduced to AH for the first time.
I can't attest to the overall percentage of GV use, but they seem to be the most prevalent way to achieve base capture. Seems in AH2, especially before the Storch, the GV game was mostly limited to spawn camp battles.
Players spend about one quarter of their time in vehicles. The peak (so far) was reached end 2016 with about 28%, since then it dropped a bit (last tour 22%)
In AH2, bases just got attacked (and captured by vehicles as today. One of the main reasons of the gradual increase of the capture share is that the terrains were made more and more Gv friendly. For example Mindanao & Baltic had far less GV spawns back in the day. We had maps like Ozkansas and others which had many places you could only reach by goon at all.
Also spawn camp battles and TT were more prominent because of a) player numbers and b) terrains changes over the years. There's much less GV vs Gv combat in AhIII because of the terrain. In many places, tanker suddenly had a hard time finding each other.
When the GV control system was changed in 2010, GV's did in fact become more popular, because of the much increased accessibility. But that boost was not that massive at all, for the most part it recovered some ground lost (in terms of gametime) that occured in 2009-2010.