I would be interested in this as well. However, I think, that exchanges are rather cautious when announcing new pair support before hand. Better availability will most probably raise volume and/or price, therefore major exchanges announcing "coin XY added soon" might be a serious buy/mine signal (e.g. one could buy given coin from creators website, etc). So exchanges would directly affect market by doing so. Also, like @youniversal-1ove outlined, this kind of information might lead up to mindless buy/mine and sooner or later, one will end up with wallet full of scamcoins.
I am sure, that major exchanges do a solid research before adding any new pair, but they are not safe from human error.