I would expect the game to sell well, slow at first then build up speed.
There are a few things holding the sales back right now:
1) While Elite started it all, it is not well known. It was never as popular as the Wing Commander games or Privateer games. Remember Wing Commander was on multiple console as well as PC, and it released many games over the course of many years. While Elite came out before most people even had PC's. So while there are some people that remember playing Elite, there are far more that remember Wing Commander games. It is nostalgia that is driving early sales.
2) People don't like paying just to play the Alpha or Beta, let alone the prices asked for with ED. If ED had much lower price points it would have sold much better. Also if you look at what you get for those high prices with ED you don't much in the way of extra's. It is the extra's that convince people to shell out more. This is something that ED did perhaps poorly but SC did amazing well at. If you compare what you get with SC starter package and the minimum ED package, you get way more with SC. Also SC has ignored the possibility of selling expansions in the future while ED is upfront with the fact that there will be expansions. Purchasing SC is a much better "deal" (assuming that they deliver a quality product and all features). Even right know in order to play you have to spend $100 over the base game (yes you get the expansion pass but not everyone likes buying those). What this also does is make it so that their is no real incentive to purchase early, so you might as well wait for it to be released and find out then. Everyone thank X-rebirth for creating ****** off costumers.
Now then how will these things change?
The exposure from the alpha and beta, especially the July 29th beta will draw in many people. If you are interested in space games you will check out ED and if it looks cool you are far more likely to spend the extra $25 to purchase and play now, or just pre-order the base game and get early access (something Frontier really needs to highlight). Now then when the game launches its going to be seen as a normal price, driving more people to buy vs spending extra just to play early. Game reviews and previews of the Beta will promote the game to no end, again driving up sales.
And finally SC will end up helping ED sales. Currently the AC is a little disappointing, even if CIG fix its problems it has limited appeal as a arena style game. Even assuming that CIG can get multiplayer ships into AC by the end of the year (with CIG's track record its seems very unlikely), the game play will drive get people into the mood to play a Space sim. With the launch of SC so far away, people will want to play a Space sim in the mean time, again driving sales up for ED.
If Frontier make a good game, I see ED selling very well (not mainstream well).
