This statement is inaccurate from a statistical stand point, there is absoulitly no guarantee that the number of users who have enough merit but suffer lack of activity is going to increase.

There is a good possiblity it is going to decrease, remain somehow the same, or simply follow your prediction.

By all means i don't think any changes are required for now, despite the fact that i always have more merits than activity, i personally think it's fun, i will most likely be a legendary merit wise  before becoming hero activity wise which is fine by me as long as i get all the privileges a legendary gets