There most definitely is an "end game" in every sandbox game.
Ever play Star Wars Galaxies? I stopped before Jump to Lightspeed came out but when I played it I was one of the most wealthy Bounty Hunters on my server. That class template could generate ridiculous amount of coin if you knew how to exploit the game mechanics which I did. I then used that money to invest in vast mining fields. It got to such a ridiculous point that I actually just stopped because there was no need for me to make more money ever again or for anyone I ever played with. I was literally a bank to myself lending money to help friends kickstart their own little business ventures. To me that was end game. The only real raid we did was hunting Rancors and Jedi before they fucked up the whole system and I quit.
In some games you make up your own end game. The only difference in this regard between SWG and EVE is EVE gives you more options to define your own "end game" including controlling planets/space.
There is currently a debate in the SC community about what if any control mechanic should be implemented and how after one of the Devs asked for feedback on what the community's thoughts were. The biggest part of the debate is should players have just influence over NPCs controlling planets and allow planets to exchange hands or should players ever own them. If any is implemented that could be considered "end game".
Exploration, once implemented, could have an end game by finding something unique that only that player could ever get or find in game. Same is apparently planned for Research.
On the personal combat side "end game" could be finding unique bosses like a space pirate that has been making news reports that you and your friends can take down and once they are dead they are dead for good.
On more broad terms Chris mentioned that they hope to allow the Vanduul to launch invasions that players are then encouraged to help participate in which could be providing a hospital ship (spawn point), running cargo missions to effected planets under fire and of course direct combat helping the UEE and maybe other races battle the Vanduul.
Finally you could be a pirate. For some that will be their "end game". Some people get a thrill from hunting rich cargo and players while dodging a military and police bent on killing them in large parts of the galaxy with bounty hunters looking for them everywhere. Part of that piracy system is actually already in game in 2.5 just not fully fleshed out until the first full pass of that job in 3.0.
So those are examples of possible "end game" gameplay one might expect from SC. So I agree with you and others that there is a legitimate concern with players on Day 1 getting things like Super Hornets and Constellations.
Having said this SC is primarily a skill based game vs some type of linear power curve game like EQ. It is after all an FPS game first and foremost. A pirate in a Super Hornet jumping a skilled player in a starter ship is going to have their face pushed in and will be lucky to make it out alive.
Honestly Piracy is going to be your biggest issue in SC with these ships. Really good players going pirate and just raping and pillaging people. The thing is there are far larger organizations with significantly larger fleets of ships that are slated to play bounty hunters and mercs for hire.
The one thing I'm super glad about is that both Piracy and Bounty Hunting as jobs are getting a first pass treatment in 3.0. We will actually get a chance to see how that mechanic will work.
With Mercenary also going in with 3.0 players will be able to hire people to escort them right off the bat. Early on nobody is going to have any real money so people will just help escort you around for simply a cut of your profits. I'm not sure if the Uber rating mechanic is going in (I don't think so) but at some point players will be able to rate you so that's further incentive to do well as a Merc or really any job.