Given that...
[1] - Ether probably caught the last bus on major contenders
[2] - It's almost un-contested in its space
[3] - Its developer and promotional base now has bucket loads of money and growing
[4] - It has yet to go on any of the big-3 Chinese exchanges which now seems only a matter of time given the trading volume it has on current "poxy" exchanges
[5] - It's probably about to get a mainstream media/BBC/WSJ splash along the lines of "New Contender Gives Bitcoin a Run for Its Money"
[6] - Hundreds of media pundits have been saying for years that they think that "Cryptocurrencies are the future but bitoin's not the one" and that this is probably their last chance to save face
[7] - This is the leading edge of the "Fill Your Car up Using Smart Contracts Base on the Ethereum Network" type news surprises rather than the trailing edge
[8] - Litecoin reached the same ratio of Bitcoin's marketcap that Ethereum has now - except with only 1 developer
... I'd say that a conservative justifiable valuation might be, say 15% of Bitoin's marketcap for a start, wouldn't you ? (At least not unreasonably)
That's still a doubling from here.