Ethereum won't last long. As soon as someone will provide users with better technology they'll switch, as the important part of using Ethereum is using other based-on cryptocurrencies. For bitcoin, tho, because it is first and is the most recognized one, the future shines bright. Especially with the trend of illegalizing ICO's.
But nowadays only Ethereum have great experience of working with other altcoins, smart-contracts and problem solving. So, no matter what other project and experts say, today we haven't got any alternative for Ethereum.
P.S: Ether blockchain isn't ideal, but its team have already solved a lot of problems, and would do it again and again.