Nvidia has not increased bus width from the Kepler generation at each product tier. In fact they have reduced bus width with GM106 (128 bit) compared to GK106 (192 bit). Nvidia have been able to feed their GPUs by increasing memory speeds GDDR5 (from 6 Gbps -> 7 Gbps -> 8 Gbps) / GDDR5X (1/11 Gbps) and with improved color compression. Thats why I am quite sure Nvidia will stick to the same memory bus width.I assumed that increase in bus width is what is required to properly fed GV architecture, and each generation Nvidia increases the amounts of VRAM available in specific price tiers, and also increased the memory bus width.
For example if they decide to use GV107 with 192 Bit GDDR5X, they can for example offer something like this:
GTX 2050 Ti - 6 GB GDDR5X
GTX 2050 - 3 GB GDDR5. In both cases it would be improvement over the GPUs they replaced. GDDR5X memory controller is backwards compatible with GDDR5.