It would take a miracle for the DA to get to even terms by 2020, its more likely that they may reach 30%. They have been growing steadily but not quickly enough and inroads into more and more of the public will get harder. They have also failed to expand at a sufficient growth in many provinces like KZN. Political forecasts are just random guesses at best, they predicted that COPE would increase market share, which it didnt and they never thought that the NFP(I think, the splinter group off IFP) would win any wards.
I pray for the day when we have an equallly fought election but don't think it will be anytime soon.
I have not seen the COPE forecasts you have seen, I have just seen the internal DA forecasts. So far the forecasts have been fairly accurate (as I pointed out, the DA got more municipalities than it forecast in the last elections).