It really is limited how much more Dogecoin can grow in value unless it gets more mainstream attention. Dogecoin's large supply works against it, so it needs a considerable boost in marketcap before that is possible and for that to happen it also needs a considerable liquidity injection. Personally speaking, I think Dogecoin is too late to invest in, there are ICOs and other cryptocurrencies that can give you a better ROI than dogecoin.