I know I am not qualified to answer this ..... but nether the less, heres my opinion.
Whilst I earnestly hope that someone will give Wolfman a list of makers whose work will double in value (so I can write them down myself!), my belief is that you will not find a consensus - it will always be a gamble. Admitedly some people are able to study "form", and predict outcomes better than others, thereby reducing the risks - but it is still uncertain.
If it was not uncertain, then given todays free exchange of information, everybody would be buying the "perfect investment knives" - the ones that everyone agrees will increase in value. Soon, however the current price would soon rise to a value whereby future gains are much less.This is a process, which if my memory serves me correctly, is called arbitrage, and applies to all forms of trade and valuation (as advocated by Modigliani and Miller).
Having said all this, scarcity of capital, and also scarcity of supply mean that certain people, with the right funds, at the right time, are able to make killer purchases - but they do this by having information others don't - eg. knowing when a piece is going to be sold and by whom.
Outside of this example I think we all take a calculated risk when we make an investment. The higher the risk the higher the potential returns or the potential losses. So in my mind going with the newer maker with an uncertain future may well offer the highest return if it goes well - but the chances are lower than say buying a Loveless or Moran at todays prices - however here the % increase on the latter will be lower.
In the short to medium term doubling your money is a big return - in my mind it means taking a big risk - which probably means not buying from the maker that everyone thinks will double in value.
The other way to earn a return is to invest in the thing some people are willing to pay a premium for - time. Getting on the list of a maker with a wait of several years means that at some point you will take delivery of a piece other people will have to wait several years for (the key here is that you have taken the chance that the maker will still be as hot when the piece arrives.) many people will pay you a premium over your purchase price to avoid the wait.
...... Oh my what a ramble - I'm going to bed!
Stephen