I think whattomine.com isnt speculating about future prices.. and assumes you are cashing out weekly. If you have a firm belief that ethereum will go up; then keep mining it and just hold onto those coins. Alternatively, (depending on the profit margin with ETC) It might still be worth mining ETC and then converting it to ethereum at an exchange. Just note If your US there are new tax laws involving exchange of digital currencies.. that may eat away at those 'profits'