Most of the GPU mining takes place in multipools these days and with the right equipment and possibly low electricity costs it can still be profitable to mine Dash
With Dash's increase in BTC & USD it gets even more profitable these days despite the high mining difficulty. Over time the block rewards will get lower and lower
but for the next few years GPU mining will continue as is, untill one day ASIC's or other forms of specialised equipment get developed because it gets profitable to do so by then.
That is at least my vision on it.