They could easily add 5 or 10 levels and give every second of the 6 rows a fourth talent. They could also add a fourth talent in the 3rd and 6th row. Or in every row. Or make a 7th after the next 10 levels.
Or maybe change nothing and instead do something major to the Glyph system. They can do whatever they want, so just saying "15 new levels because of talent" is kinda stupid.