I am betting that Elite 4 will not happen for some of the following reasons...
1) There are already a myriad of space trading games; the 'X' games and Eve online spring to mind. Elite 4 would have to compete with these recent games and I think that it's a lack of confidence that they could better.
2) Unfortunately most games these days have to be established franchises or movie tie ins to justify the development costs; GTA, FIFA, etc. Although Elite is well know by gamers 25+ it would just be regarded as another game by most and would have to be something extra special to get people to buy it. The cost of development for games now is very high and difficult with a smaller development company.
3) The failure of Elixir Studios who tried to create something special with 'Republic: Revolution' and the recent aquisition of Lionhead has shown that it's a very tough market for creative and innovative games studios. Well done to Frontier for producing 'Dog's Life', but I suspect the sales figures weren't great.
So, sadly Elite 4 won't happen.